Orthopedics

Feature Articles 

Subvastus and Medial Parapatellar Approaches in TKA: Comparison of Functional Results

Julian Dutka, MD, PhD; Michal Skowronek, MD; Pawel Sosin, MD, PhD; Pawel Skowronek, MD

Abstract

The purpose of this study was to compare the clinical results of total knee arthroplasty (TKA) in the early and late postoperative period using subvastus and medial parapatellar approach. A prospective randomized controlled study was conducted in a group of 169 patients (180 TKAs) with 2-year follow-up. Patients were divided into a study group (97 TKAs) with a subvastus approach and a control group (83 TKAs) with a parapatellar approach. Assessment of the results of both operating approaches was based on functional, clinical Knee Society Score, and pain (visual analog scale). Patients in the subvastus group achieved full active extension, better range of motion, and better Knee Society Score results at 12 days, 6 weeks, and 12 weeks earlier than patients in the medial parapatellar group. They also had less pain at 12 days. No statistically significant differences existed between assessed end points in both groups at 24- and 52-weeks, and 24-months postoperatively. The subvastus approach has given patients better early clinical results; however, at longer follow-up, both groups had similar outcomes. The potential benefits of the subvastus approach are: protection of the extensor mechanism from damage, less risk of damaging the blood supply to the patella, earlier clinical recovery, and less pain in the early postoperative period. The subvastus approach is an alternative to the standard medial parapatellar approach in TKA. It can be used with equally good results, especially taking into consideration positive clinical aspects in the early postoperative period.

Drs Dutka, Skowronek (Michal), Sosin, and Skowronek (Pawel) are from the Department of Orthopedic and Traumatologic Surgery, Zeromski Hospital, Cracow, Poland.

Drs Dutka, Skowronek (Michal), Sosin, and Skowronek (Pawel) have no relevant financial relationships to disclose.

The subvastus approach in total knee arthroplasty (TKA) was described by Hofmann et al 1 in 1991. In the beginning, this approach was not popular because of limited insight into the operative field and problems with everting patella. Many surgeons have used this approach successfully since then and it has been supported by a number of publications. 2–4 It is well known that the operating approach is essential to the clinical result of TKA. The subvastus approach is regarded as an alternative to the standard medial parapatellar approach. 5 Many authors have emphasized the potential benefits of the subvastus approach, which are keeping the extensor mechanism undamaged, less risk of blood supply damage to the patella, earlier clinical recovery, and less pain in the early postoperative period. The purpose of this study was to compare results of TKA using the subvastus and medial parapatellar approaches in the early and late postoperative periods. The early period was defined as 24 weeks after TKA and the late period was defined as between 24 weeks and 24 months postoperatively. Advantages of both operating approaches were assessed according to clinical and radiological results.

Between 2004 and 2008, a prospective, randomized trial including 169 patients with 180 TKAs was performed in our hospital. Most of the patients had advanced stage osteoarthritis with deformation of the knee attributed to delay in surgical decision and a long waiting period until surgery.

Patients were divided into 2 groups. Group 1 included patients with odd numbers in the medical file who underwent a subvastus approach. Group 2 included patients with even numbers in the medical records who underwent the medial parapatellar approach. Groups 1 and 2 were homogenous regarding age, gender, cause of surgery, preoperative clinical state, and type of implanted knee system.

The inclusion criteria were idiopathic osteoarthritis and absence of previous osteotomies. The exclusion criteria were prior knee surgery, injury of a knee, and damage of the extensor mechanism.…

Abstract

The purpose of this study was to compare the clinical results of total knee arthroplasty (TKA) in the early and late postoperative period using subvastus and medial parapatellar approach. A prospective randomized controlled study was conducted in a group of 169 patients (180 TKAs) with 2-year follow-up. Patients were divided into a study group (97 TKAs) with a subvastus approach and a control group (83 TKAs) with a parapatellar approach. Assessment of the results of both operating approaches was based on functional, clinical Knee Society Score, and pain (visual analog scale). Patients in the subvastus group achieved full active extension, better range of motion, and better Knee Society Score results at 12 days, 6 weeks, and 12 weeks earlier than patients in the medial parapatellar group. They also had less pain at 12 days. No statistically significant differences existed between assessed end points in both groups at 24- and 52-weeks, and 24-months postoperatively. The subvastus approach has given patients better early clinical results; however, at longer follow-up, both groups had similar outcomes. The potential benefits of the subvastus approach are: protection of the extensor mechanism from damage, less risk of damaging the blood supply to the patella, earlier clinical recovery, and less pain in the early postoperative period. The subvastus approach is an alternative to the standard medial parapatellar approach in TKA. It can be used with equally good results, especially taking into consideration positive clinical aspects in the early postoperative period.

Drs Dutka, Skowronek (Michal), Sosin, and Skowronek (Pawel) are from the Department of Orthopedic and Traumatologic Surgery, Zeromski Hospital, Cracow, Poland.

Drs Dutka, Skowronek (Michal), Sosin, and Skowronek (Pawel) have no relevant financial relationships to disclose.

Correspondence should be addressed to: Julian Dutka, MD, PhD, Orthopedic and Traumatologic Department of Zeromski Hospital, Os Na Skarpie 66, 31-913 Cracow, Poland (jdorttra@interia.pl).
Posted Online: June 14, 2011

The subvastus approach in total knee arthroplasty (TKA) was described by Hofmann et al 1 in 1991. In the beginning, this approach was not popular because of limited insight into the operative field and problems with everting patella. Many surgeons have used this approach successfully since then and it has been supported by a number of publications. 2–4 It is well known that the operating approach is essential to the clinical result of TKA. The subvastus approach is regarded as an alternative to the standard medial parapatellar approach. 5 Many authors have emphasized the potential benefits of the subvastus approach, which are keeping the extensor mechanism undamaged, less risk of blood supply damage to the patella, earlier clinical recovery, and less pain in the early postoperative period. The purpose of this study was to compare results of TKA using the subvastus and medial parapatellar approaches in the early and late postoperative periods. The early period was defined as 24 weeks after TKA and the late period was defined as between 24 weeks and 24 months postoperatively. Advantages of both operating approaches were assessed according to clinical and radiological results.

Materials and Methods

Between 2004 and 2008, a prospective, randomized trial including 169 patients with 180 TKAs was performed in our hospital. Most of the patients had advanced stage osteoarthritis with deformation of the knee attributed to delay in surgical decision and a long waiting period until surgery.

Patients were divided into 2 groups. Group 1 included patients with odd numbers in the medical file who underwent a subvastus approach. Group 2 included patients with even numbers in the medical records who underwent the medial parapatellar approach. Groups 1 and 2 were homogenous regarding age, gender, cause of surgery, preoperative clinical state, and type of implanted knee system.

The inclusion criteria were idiopathic osteoarthritis and absence of previous osteotomies. The exclusion criteria were prior knee surgery, injury of a knee, and damage of the extensor mechanism. All operations were performed by 1 surgeon (J.D.) using 1 type of implant (ie, PFC Sigma [DePuy, Warsaw, Indiana], cruciate retaining TKAs in 145 cases, and posterior stablilized TKAs in 35 cases. In all cases, the patella did not resurface. Demographic and clinical data are presented in Table .

Mean and Percentage Values for Baseline Demographic and Clinical Data

Table 1. Mean and Percentage Values for Baseline Demographic and Clinical Data

The hospital stay was 12 days and the standard protocol of early rehabilitation was used to achieve good range of motion, decrease in pain, and improvement of extensor mechanism function.

The skin incision in the study group was performed at 30° of knee flexion and started medially and 5 to 6 cm above the upper pole of the patella and continued along the medial border of the patella to the medial limit of the tibial tuberosity. Arthrotomy started above the upper medial pole of the patella and continued along the patella, leaving the appropriate margin of a synovial capsule and farther down to the tibial tuberosity. The proximal part of the arthrotomy extended medially and proximally, along the edge of the vastus medialis. Using blunt dissection, the vastus medialis was then retracted proximally and laterally while maintaining its attachment to the patella without everting it. 1

In the medial parapatellar group, the knee was approached in flexion using straight incision over the patella starting 4 to 5 cm above its upper pole. Arthrotomy started in the medial part of the quadriceps aponeurosis and was carried out distally across the joint line and parallel to the medial border of the patellar tendon and reaching the level of the tibial tuberosity. 6 All patients underwent spinal anesthesia and the same schedule of pain control was applied in the postoperative period. On days 1 and 2, patients received opiates and later, nonsteroidal anti-inflammatory drugs. In both groups, thromboprophylaxis was carried out for 30 days postoperatively using 40 mg enoxoparine subcutaneously.

After postoperative day 1, patients in both groups were rehabilitated using an identical program, which included the use of continuous passive motion, active exercises, and walking exercises twice daily under the supervision of an experienced physiotherapist. After discharge from the hospital at 12 days, patients continued rehabilitation at home according to the same rehabilitation protocol, which included walking with full weight bearing, quadriceps muscle strengthening, and range of motion exercises.

Patients and physiotherapists were blinded on randomized results. For accurate assessment of the extensor mechanism function, knee flexion, flexion contracture, extension lag, and pain were measured at 12 days, at 6, 12, 24, and 52 weeks and at 24 months postoperatively. The additional comprehensive assessment was carried out based on clinical and functional Knee Society Scores. Geometrical positions of the implants were assessed on the postoperative radiograph on the day of surgery. For accurate assessment of return of extensor mechanism function, extension lag was defined as active extension deficiency and fixed flexion contracture was defined as lack of active and passive extension.

Statistical analysis of the results was performed by U-Manna-Whitney test, the Pearson’s chi square test, and Fisher’s test. Significance was determined at P<.05.

Results

In the presented material, the study group achieved better clinical results in the early postoperative period. At 12 weeks postoperatively, results in both groups were comparable and no substantial statistical differences were observed. Detailed results of end points presented as follows.

Postoperative knee flexion in both groups showed no substantial statistical differences. At 6 weeks postoperatively, flexion contracture of the knee was present in 8.3% patients in the subvastus group and in 19.7% of patients in the medial parapatellar group. Later, substantial differences were not observed. The greatest differences observed were in quadriceps muscle strength, most important in active extension of the knee. In the study group, a smaller percentage of the active extension deficiency was observed. It amounted to 9.3% of cases after 12 days, 2.1 % of cases after 6 weeks, and 1% of cases after 12 weeks. In the control group, those values were 48.2%, 24.7%, and 12.3%, respectively. These differences were statistically significant. At further follow-up, no substantial differences were observed in the active extension deficiency in either group.

The essential, beneficial influence of the subvastus approach on pain was observed in the initial period of observation. At 12 days after TKA, the day of discharge, the average visual analogue scale result was 3.0 points. However, in the control group it was 3.9 points after 12 days. Differences were statistically significant. The level of pain assessed at 6-week follow-up postoperatively was comparable and showed no substantial differences (Tables –). Mean postoperative clinical score measured in the Knee Society Score in the study group was 76.8 after 12 days and 104.4 after 6 weeks. Similar scores in the control group were 65.7 and 92.9, respectively. Differences were statistically significant. At 12-, 24-, 52-week and 24-month follow-up, no significant differences were found (Table ).

Percentage Values for Longitudinal Outcomes for the Subvastus and Medial Parapatellar Groups

Table 3. Percentage Values for Longitudinal Outcomes for the Subvastus and Medial Parapatellar Groups

In 96 patients in the study group and 83 knees of the control group, correct anteroposterior and lateral implant positions were achieved. In the subvastus group, one patient had a knee implant in malposition (5° valgus of the tibial component). 7 Prolonged intrarticular hematoma appeared in the subvastus group in 5 patients (5.4%) and in the medial parapatellar group in 4 patients (4.7%). Other complications prolonged wound healing such as partial necrosis and venous thromboses, which were similar in both groups. Deep infection appeared in 1 patient in the medial parapatellar group and was excluded from the study after 12 weeks of observation (Table ).

Percentage of Complications After Subvastus or Medial Parapatellar Approach

Table 4. Percentage of Complications After Subvastus or Medial Parapatellar Approach

Discussion

In TKA, certain surgical approaches allow insight in the operating field to the extent and atraumatic operative techniques that may influence the function of the extensor mechanism. The presented study showed essential statistical differences in clinical parameters of the subvastus approach compared to the medial parapatellar approach in the early assessment period. The main advantage of this approach was to save the extensor mechanism as evidenced by better range of motion and less reports of pain up to 12 weeks postoperatively.

Our patients who underwent the subvastus approach in the early postoperative period achieved better active extension of the knee after 12 weeks; differences between groups were not observed. Hofmann et al 1 had a similar observation. They emphasized that the subvastus approach was more anatomical than the medial parapatellar approach because it preserved the integrity of the extensor mechanism. 1 Maric et al, 2 in the first clinical evaluation of the subvastus approach, compared it with the median parapatellar approach in 41 patients undergoing primary TKA. The patients who underwent the subvastus approach could, on average, perform straight leg raising 4 days sooner than patients who underwent the medial parapatellar approach. 2 Faure et al 8 were the first to evaluate the subvastus approach in 1-stage bilateral arthroplasties. Quadriceps strength was initially greater in patients who underwent the subvastus approach but was equal in both groups at 3 months. Patients preferred the subvastus approach at 4:1 to the median parapatellar approach. 8

Saving vascular supply to the patella is an essential advantage of the subvastus approach. It was also stressed in the publications of Hofmann et al, 1 Bjorkstrom and Goldie, 9 and Roysam and Oakley. 10 Another clinical advantage of the subvastus approach is less postoperative pain. In our study, at 12 days postoperatively, patients reported less pain while carrying out exercises according to the rehabilitation protocol. In the Maric et al 2 trial, patients in the sub-vastus group took 40% fewer painkillers and the duration of hospitalization was 3 days shorter. Another benefit of the subvastus approach anatomical is tracking preservation of the patella.

In the studied material differences in the radiological assessment, incorrect implantation was not found. Bindelglass and Vince 11 evaluated patellar tilt and subluxation with the subvastus approach and found no significant difference in patellar tracking between approaches, however, they found that less lateral releases were performed in patients in the subvastus. In our study, we found no substantial differences in knee flexion depending on the operating approach. Similar observations were presented by Sastre et al, 12 however, better mobility results appeared in the subvastus in connection with less knee pain. 12

The subvastus access has certain limitations. The presence of scars after earlier knee arthrotomies should be a contraindication to the subvastus approach. Based on our experience and different authors, the subvastus approach is not beneficial in revision surgery because of worse insight. 13 Many authors are emphasizing that the subvastus approach should be applied in primary TKA rather than revision because the limited insight into the operative field caused problems with everting patella. 14 Additionally, Hofman et al 1 do not recommend this approach for patients weighing more than 85 kg, due to worse insight into the operative field. In et al 15 noticed problems in TKA for obese patients and do not recommend the subvastus approach when the circumference of the thigh is >55 cm. We had no problems with operative inspection in obese patients in our study. However, we found that a subvastus approach and access to the knee were limited by flexion contracture of the knee in accordance with the conclusions of Faure et al. 8 This approach is not recommended for obese patients and with knee contracture.

Choice of operating approach had no influence on the frequency of general and local complications and a similar percentage of complications had no significant influence on the results in both groups. Based on our experience, the subvastus approach is an alternative to the standard, most often applied medial parapatellar approach in TKA and can be used with equally good results, especially taking into consideration positive clinical aspects in the early postoperative period.

References

  1. 1. Hofmann AA, Plaster RL, Murdock LE. Sub-vastus (Southern) approach for primary total knee arthroplasty. Clin Orthop Relat Res. 1991; (269):70–77.
  2. 2. Maric Z, Ott DM, Karpman RR. The standard versus the sub-vastus (southern) approach for total knee arthroplasty: a randomised prospective study. Orthop Trans. 1991; 15(1):43.
  3. 3. Bridgman SA, Walley G, MacKenzie G, Clement D, Griffiths D, Maffulli N. Sub-vastus approach is more effective than a medial parapatellar approach in primary total knee arthroplasty: a randomized controlled trial [Published online ahead of print January 9, 2009]. Knee. 2009; 16(3):216–222. doi: 10.1016/j.knee.2008.11.012 [CrossRef]
  4. 4. Weinhardt C, Barisic M, Bergmann EG, Heller KD. Early results of subvastus versus medial parapatellar approach in primary total knee arthroplasty [Published online ahead of print May 7, 2004]. Arch Orthop Trauma Surg. 2004; 124(6):401–403. doi: 10.1007/s00402-004-0692-3 [CrossRef]
  5. 5. Abbot LC, Walter F, Carpenter WF,. Surgical approaches to the knee joint. J Bone Joint Surg Am. 1945; 27(2):277–310.
  6. 6. Lotke PA. Anterior medial exposures. In: Lotke PA, ed. Master Techniques in Orthopaedic Surgery: Knee Arthroplasty. New York, NY: Raven Press; 1995:3–14.
  7. 7. Bach CM, Steingruber IE, Peer S, Nogler M, Wimmer C, Ogon M. Radiographic assessment in total knee arthroplasty. Clin Orthop Relat Res. 2001; (385):144–150 doi: 10.1097/00003086-200104000-00022 [CrossRef]
  8. 8. Faure BT, Benjamin JB, Lindsey B, Volz RG, Schutte D. Comparison of the subvastus and paramedian surgical approaches in bilateral knee arthroplasty. J Arthroplasty. 1993; 8(5):511–516. doi: 10.1016/S0883-5403(06)80216-0 [CrossRef]
  9. 9. Bjorkstrom S, Goldie IF. A study of the arterial supply of the patella in the normal state, in chondromalacia patellae and in osteoarthritis. Acta Orthop Scand. 1980; 51(1): 63–70. doi: 10.3109/17453678008990770 [CrossRef]
  10. 10. Roysam GS, Oakley MJ. Subvastus approach for total knee arthroplasty: a prospective, randomized, and observer-blinded trial. J Arthroplasty. 2001; 16(4):454–457 doi: 10.1054/arth.2001.22388 [CrossRef]
  11. 11. Bindelglass DF, Vince KG. Patellar tilt and subluxation following subvastus and parapatellar approach in total knee arthroplasty. Implication for surgical technique. J Arthroplasty. 1996; 11(5):507–511. doi: 10.1016/S0883-5403(96)80101-X [CrossRef]
  12. 12. Sastre S, Sanchez MD, Lozano L, Orient F, Fontg F, Nuñez M. Total knee arthroplasty: better short-term results after subvastus approach: a randomized, controlled study. Knee Surg Sports Traumatol Arthrosc. 2009; 17:1184–1188. doi: 10.1007/s00167-009-0780-6 [CrossRef]
  13. 13. Khan RJK, Keogh A, Fick D, Wood D. Surgical approaches in total knee arthroplasty. (Protocol) Cochrane Database System Rev. 2005; 2.
  14. 14. Ogata K, Ishinishi T, Hara M. Evaluation of patellar retinacular tension during total knee arthroplasty. Special emphasis on lateral retinacular release. J Arthroplasty. 1997; 12(6):651–656. doi: 10.1016/S0883-5403(97)90138-8 [CrossRef]
  15. 15. In Y, Kim JM, Choi NY, Kim SJ. Large thigh girth is a relative contraindication for the subvastus approach in primary total knee arthroplasty [Published online ahead of print March 9, 2007]. J Arthroplasty. 2007; 22(4):569–573. doi: 10.1016/j.arth.2006.06.007 [CrossRef]

Mean and Percentage Values for Baseline Demographic and Clinical Data

Group 1 (SD) Group 2 (SD)
No. of TKAs/patients 97/89 83/80
Gender, M/F 48/41 45/35
Age 70.3 (6.1) 71 (5.1)
Total KSS 77.7 (8.9) 78.3 (9.9)
Clinical KSS 41.2 (7.7) 42.6 (8.2)
Functional KSS 36.5 (4.8) 35.7 (4.6)
Flexion 111.0 (13.7) 110.8 (12.5)
Flexion contracture (%) 32.0 28.9
Active extension deficiency (%) 0 0
Pain (VAS) 7.4 (1.1) 7.2 (1.1)

Mean Values (SD) for Longitudinal Outcomes for the Medial Parapatellar and Subvastus Groups

Subvastus (SD) Medial Parapatellar (SD) P Value
Preoperative
Total KSS 77.7(8.9) 78.3 (9.9)
Clinical KSS 41.2 (7.7) 42.6(8.2)
Functional KSS 36.5 (4.8) 35.7 (4.6)
Flexion 111.0 (13.7) 110.8 (12.5)
Pain (VAS) 7.4 (1.1) 7.2 (1.1)
12 days
Total KSS 76.8 (9.7) 65.7 (10.2) .000000
Clinical KSS 57.2 (8.1) 46.7 (8.4) .000000
Functional KSS 19.6 (5.0) 19.1 (6.0) .330356
Flexion 95.6 (8.6) 94.9 (8.6) .916816
Pain (VAS) 3.0 (1.0) 3.9 (1.1) .000001
6 weeks
Total KSS 104.4 (11.2) 92.9 (12.8) .000000
Clinical KSS 66.1 (8.5) 60.7 (9.1) .000197
Functional KSS 38.3 (7.5) 32.3 (7.8) .000001
Flexion 104.8 (8.9) 105.4 (7.5) .678252
Pain (VAS) 1.6 (0.9) 1.6 (0.7) .401573
12 weeks
Total KSS 123.3 (12.4) 119.3 (12.7) .056200
Clinical KSS 73.0 (8.6) 70.7 (9.9) .091715
Functional KSS 50.4 (7.2) 48.7 (8.3) .036786
Flexion 110.4 (8.6) 111.5 (7.2 ) .410832
Pain (VAS) 0.6 (0.8) 0.7 (0.7) .243245
24 weeks
Total KSS 130.5 (11.3) 129.7 (11.5) .896850
Clinical KSS 75.1 (8.2) 74.7 (9.3) .777224
Functional KSS 55.4 (6.6) 55.0 (7.4) .744565
Flexion 113.3 (8.1) 113.6 (7.2) .655328
Pain (VAS) 0.4 (0.8) 0.1 (0.4) .555701
52 weeks
Total KSS 137.4 (10.7) 135.4 (9.8) .308292
Clinical KSS 79.8 (6.8) 79.1 (7.3) .471104
Functional KSS 57.6 (7.8) 56.3 (8.0) .205405
Flexion 114.0 (8.0) 114.9 (7.1) .376782
Pain (VAS) 0.1 (0.4) 0.0 (0.2) .770821
24 months
Total KSS 140.9 (10.8) 140.0 (10.9) .884621
Clinical KSS 80.1 (7.5) 79.6 (8.7) .765774
Functional KSS 60.9 (8.6) 60.5 (8.4) .532621
Flexion 113.8 (8.1) 115.1 (7.4) .189240
Pain (VAS) 0.2 (0.6) 0.1 (0.2) .884521
Mean Values (SD) for Longitudinal Outcomes for the Medial Parapatellar and Subvastus Groups

Table 2. Mean Values (SD) for Longitudinal Outcomes for the Medial Parapatellar and Subvastus Groups

Percentage Values for Longitudinal Outcomes for the Subvastus and Medial Parapatellar Groups

SV (%) MP (%) P Value
Preopoperative
Active extension deficiency
0 0
Flexion contraction 32.0 28.9
12 days
Active extension deficiency
9.3 48.2 .00000
Flexion contraction 18.6 20.5 .74493
6 weeks
Active extension deficiency
2.1 24.7 .00001
Flexion contraction 8.3 19.7 .02704
12 weeks
Active extension deficiency
1.0 12.3 .00204
Flexion contraction 7.4 6.2 .75380
24 weeks
Active extension deficiency
1.0 3.7 .23515
Flexion contraction 7.3 6.2 .76801
52 weeks
Active extension deficiency
1.0 3.75 .23427
Flexion contraction 10.5 7.5 .48896
24 months
Active extension deficiency
1.1 3.7 .24851
Flexion contraction 9.7 4.9 .23564

Percentage of Complications After Subvastus or Medial Parapatellar Approach

Complication SV (%) MP (%)
Intrarticular hematoma 5.1 4.8
Parietal wound necrosis 3.1 2.4
Venous thrombosis 2.1 3.6
Deep infection 0 1.2

10.3928/01477447-20110427-05

Sign up to receive

Journal E-contents