Orthopedics

Tips & Techniques 

Use of a Suture Anchor Technique to Replace the Tethering Effect of the Ligamentum Teres in the Treatment of Complex Hip Dysplasia

Steven J. Magister, MD; Raymond W. Liu, MD

Abstract

After open hip reduction in hip dysplasia, some hips can have persistent instability, even after pelvic and femoral osteotomies as well as capsulorrhaphy. While the diseased ligamentum teres in a dislocated hip is thought to contribute to inadequate reduction, the native ligament is thought to provide some level of stability. As such, the purpose of this study was to investigate the utility of a suture augment that replaces the function of the ligamentum teres to provide added stability. [Orthopedics. 2020;43(5):e480–e485.]

Abstract

After open hip reduction in hip dysplasia, some hips can have persistent instability, even after pelvic and femoral osteotomies as well as capsulorrhaphy. While the diseased ligamentum teres in a dislocated hip is thought to contribute to inadequate reduction, the native ligament is thought to provide some level of stability. As such, the purpose of this study was to investigate the utility of a suture augment that replaces the function of the ligamentum teres to provide added stability. [Orthopedics. 2020;43(5):e480–e485.]

The ligamentum teres (LT) is a well-characterized structure in the native hip that originates from the cotyloid fossa of the acetabulum and inserts on the fovea of the femoral head.1,2 While the function of the LT remains unclear, previous biomechanical studies have suggested that it contributes, at least in part, to joint stability.3,4 Specifically, it is suggested that the LT functions when it is at its tightest with the hip flexed, adducted, and externally rotated.1 Previous reports have indicated that in developmental dysplasia of the hip (DDH), the diseased LT is redundant and thickened, with excision being recommended to allow for proper reduction.5,6 However, to preserve the proposed stability that the LT offers, Wenger et al7 suggested excising the redundant portion of the LT and either suturing it back to the anterior origin of the transverse acetabular ligament or reattaching the free end to a suture anchor placed just anterior to the labrum at the anterior-inferior edge of the acetabulum. An alternative option is to completely replace the tethering function of the LT using a suture anchor, with the advantage of easier tensioning.

The authors present a technique and clinical follow-up of a reconstructive suture anchor to substitute for the LT function in the setting of complex pediatric hip dysplasia.

Materials and Methods

Inclusion Criteria

All patients who underwent corrective hip surgery with open reduction and associated suture anchoring at the authors’ institution from January 2012 to October 2018 were retrospectively collected.

Radiologic Parameters

All patients were radiographically evaluated preoperatively, at 2 weeks postoperatively, and at their final follow-up visit. Acetabular index (AI) and International Hip Dysplasia Institute grade were measured to assess the degrees of dysplasia and dislocation/subluxation, respectively (Figure 1). Additionally, avascular necrosis (AVN) of the femoral head was graded by observing the fragmentation of the femoral head ossific nucleus in conjunction with lateral and medial metaphyseal involvement as previously described by Bucholz and Ogden.8 The AI was measured in standard fashion by determining the degree between Hilgenreiner’s line and a line from the triradiate to the superolateral edge of the acetabulum. The AI was used regardless of age, as only 1 patient had a closed triradiate cartilage. In this case, the AI was estimated at the point of the triradiate scar. The center edge angle was also calculated postoperatively for all patients who presented after the age of 5 years. To describe the geographical location of the femoral head within the acetabulum, the International Hip Dysplasia Institute grading system was used over the traditional Tönnis system because it allowed for more uniform measurements in patients with severe disease that precluded measurements based off the non-ossified or necrosed femoral head.9 Briefly, the International Hip Dysplasia Institute grade is determined by identifying the position of the center of the proximal femoral metaphysis in relation to the standard Perkin’s line and Hilgenreiner’s line, as well as a line that bisects these two lines at 45° (Figure 1). Progressive grades are given from 1 to 4, with a grade of 1 correlating to a proximal femoral metaphysis that is medial to Perkins’ line and inferior to Hilgenreiner’s line and a grade of 4 given for hips in which the proximal femoral metaphysis is lateral to Perkin’s line and superior to Hilgenreiner’s line.

Representative preoperative anteroposterior radiograph of a 5-year-old boy (patient 7) with chromosomal abnormality of unknown significance with International Hip Dysplasia Institute grade 4 dislocation. The red lines designate standard Hilgenreiner’s and Perkin’s lines. The blue line is shown to complete the 4 quadrants of the International Hip Dysplasia Institute grading system. The yellow dot designates the center of the superior margin of the ossified femoral metaphysis, with the International Hip Dysplasia Institute grade based on the position of this dot, progressing from grade 1 in the inferior medial region counterclockwise to grade 4 in the superior lateral region.

Figure 1:

Representative preoperative anteroposterior radiograph of a 5-year-old boy (patient 7) with chromosomal abnormality of unknown significance with International Hip Dysplasia Institute grade 4 dislocation. The red lines designate standard Hilgenreiner’s and Perkin’s lines. The blue line is shown to complete the 4 quadrants of the International Hip Dysplasia Institute grading system. The yellow dot designates the center of the superior margin of the ossified femoral metaphysis, with the International Hip Dysplasia Institute grade based on the position of this dot, progressing from grade 1 in the inferior medial region counterclockwise to grade 4 in the superior lateral region.

Surgical Procedure

All surgeries were performed by a single fellowship-trained pediatric orthopedic surgeon (R.W.L.) as shown in Figure 2. Patients underwent a standard anterior open hip reduction. To allow for reduction, the native LT is excised and removed from its acetabular origin and femoral insertion. All other barriers to femoral head reduction are removed. Through this anterior approach, the acetabular articular surface is visualized and the cotyloid fossa palpated. A 2.9- vs 2.3-mm suture anchor with integrated nonabsorbable braided suture attached (Osteoraptor; Smith & Nephew, London, United Kingdom) is then inserted in the posterior aspect of the cotyloid fossa to avoid iatrogenic damage to the inferior limb of the triradiate cartilage, which is located more anterior (Figure 3). The size of the suture anchor varies based on patient size and is determined intraoperatively at the time of placement.

Representative drawings demonstrating the ligamentum teres suture anchoring. Dislocated hip with elongated ligamentum (A). The ligamentum teres has been removed and a suture anchor has been inserted in the posterior aspect of the cotyloid fossa to avoid the inferior limb of the triradiate, which is more anterior (B). A 2.0-mm Steinmann pin is drilled antegrade from the fovea, exiting the proximal femur, generally just distal to the greater trochanteric apophysis (C). The suture ends are then placed into two separate holes of an Endo-button (Smith & Nephew, London, United Kingdom) and tied with the hip in mild abduction (D).

Figure 2:

Representative drawings demonstrating the ligamentum teres suture anchoring. Dislocated hip with elongated ligamentum (A). The ligamentum teres has been removed and a suture anchor has been inserted in the posterior aspect of the cotyloid fossa to avoid the inferior limb of the triradiate, which is more anterior (B). A 2.0-mm Steinmann pin is drilled antegrade from the fovea, exiting the proximal femur, generally just distal to the greater trochanteric apophysis (C). The suture ends are then placed into two separate holes of an Endo-button (Smith & Nephew, London, United Kingdom) and tied with the hip in mild abduction (D).

A 3-dimensional computed tomography reconstruction image demonstrating how the inferior limb of the triradiate cartilage is at the anterior border of the cotyloid fossa. Thus, it is recommended that the suture anchor be placed near the posterior aspect of the fossa.

Figure 3:

A 3-dimensional computed tomography reconstruction image demonstrating how the inferior limb of the triradiate cartilage is at the anterior border of the cotyloid fossa. Thus, it is recommended that the suture anchor be placed near the posterior aspect of the fossa.

A 2.0-mm Steinmann pin is then passed through the fovea of the proximal femoral head at the LT footprint, generally exiting just distal to the greater trochanteric apophysis. The local soft tissues around this exit point on the proximal femur must be cleared to allow the eventual washer or Endo-button (Smith & Nephew) to seat properly on the bone. A suture passer is then placed in the drilled hole from lateral to medial and the free suture ends are passed across the proximal femur through the track created by the Steinmann pin. At this point, pulling the two separate suture strands superiorly and inferiorly should reduce the hip joint and hold it in a stable position. Of note, in 2 hips, the tunnel for the suture anchor was instead drilled in a retrograde fashion, which has the advantage of not requiring capsulorrhaphy in the case of a reducible hip but has the disadvantage of less accurate passage of the reconstruction at the fovea and cotyloid fossa. The femoral and acetabular osteotomies are then performed as appropriate. With the femoral head reduced and the hip in slight abduction, the free ends of the suture are then tensioned and tied to the outer surface of the proximal femur over a washer (initially used) vs an Endobutton (subsequently used and preferred). The hip is ranged into abduction and adduction to ensure radiographic stability (Figure 4). The capsule is then closed in standard fashion and wounds are closed. Postoperatively, patients are kept immobilized in a spica cast for at least 6 weeks.

Serial intraoperative fluoroscopic radiographs of a 6-year-old girl (patient 9) after reconstruction demonstrating the stability of the suture anchor with no notable subluxation when the hip was ranged into mild adduction and abduction.

Figure 4:

Serial intraoperative fluoroscopic radiographs of a 6-year-old girl (patient 9) after reconstruction demonstrating the stability of the suture anchor with no notable subluxation when the hip was ranged into mild adduction and abduction.

Results

A total of 10 hips (9 patients) were identified in the retrospective review (Table 1). Average age at initial presentation was 7.2 years (range, 1–21 years), with 4 of 9 patients being male. Eight of 9 patients had neuromuscular, syndromic, or postfemoral lengthening–related dysplasia. The remaining patient had Down syndrome and recurrent dislocations secondary to global joint laxity in the setting of normal acetabular geometry and without previous open reduction. Seven patients presented with other significant lower extremity deformities on the operative extremity. Four patients presented following previously failed femoral/acetabular correction. One of 4 included a previous LT suture anchoring in the setting of femoral and acetabular osteotomies. This patient had recurrent dislocation secondary to Gross Motor Function Classification System V cerebral palsy (spastic quadriplegia).

Demographics and Pre- and Postsurgical Interventions

Table 1:

Demographics and Pre- and Postsurgical Interventions

Pre- and postoperative radiographs and corresponding measurements are shown in Figure 5 and Table 2, respectively. The mean preoperative AI and International Hip Dysplasia Institute grade were found to be 38.9°±11.4° and 3.7±0.9, respectively. At the initial postoperative appointment, the mean International Hip Dysplasia Institute grade was found to be 1.7±0.7. At final follow-up, the mean AI and International Hip Dysplasia Institute grade were 29.9°±8.7° and 1.6±0.8, respectively. The mean postoperative center edge angle was found to be 31.2°±7.7°. Three of 10 hips showed worsening of AVN by one grade. The remaining hips did not demonstrate any increased rates of AVN. Two of 10 hips required a revision surgery for recurrent subluxation. Average follow-up was 24.8 months from the time of the index procedure.

Serial anteroposterior pelvic radiographs of a 6-year-old girl (patient 9) with International Hip Dysplasia Institute grade 4 treated with femoral and acetabular osteotomies as well as suture anchoring. Of note, suture anchoring was performed in a revision setting after an early redislocation 1 day following the index procedure. Preoperative (A), 8 days postoperatively (B), 6 months postoperatively (C), and final follow-up (4.5 years from index procedure) (D) after subsequent hardware removal and lengthening and angular correction of the femur.

Figure 5:

Serial anteroposterior pelvic radiographs of a 6-year-old girl (patient 9) with International Hip Dysplasia Institute grade 4 treated with femoral and acetabular osteotomies as well as suture anchoring. Of note, suture anchoring was performed in a revision setting after an early redislocation 1 day following the index procedure. Preoperative (A), 8 days postoperatively (B), 6 months postoperatively (C), and final follow-up (4.5 years from index procedure) (D) after subsequent hardware removal and lengthening and angular correction of the femur.

Pre- and Postoperative Radiographic Measurements

Table 2:

Pre- and Postoperative Radiographic Measurements

Discussion

After open hip reduction, redislocation rates remain high, reportedly ranging from 8% to 14% based on underlying etiology and surgical approach.10–13 Although the LT is almost universally removed during open reduction, its biomechanical contribution to hip stability is still poorly understood. There have been numerous studies that have examined the biomechanical and histologic characteristics of the LT in both the normal and dysplastic hip.1,3,4,14 Biomechanical study by Wenger et al4 found native porcine LT to have a mean tensile strength of nearly 900 N. Additionally, the normal LT is histologically organized into well-differentiated collagen bands.14 Conversely, in pathologic DDH, the LT has been shown to be both grossly dysplastic and redundant as well as atrophied and metaplastic histologically.5,14,15

Assuming the native LT confers some degree of hip stability, Wenger et al7 examined the utility of removing the redundant portion of the LT during open reduction rather than excising it in its entirety. Following removal of the redundant portion off the cotyloid fossa, the free end (still attached to its femoral head insertion) is either repaired to the anterior origin of the transverse acetabular ligament or attached via suture anchor just anterior to the labrum at the anterior-inferior edge of the acetabulum. They reported no redislocation or need for secondary surgery in both their medial and anterior hip reductions. Additionally, Bache et al16 described only 3 redislocations in 109 dislocated hips with a LT to capsule tenodesis during medial open reduction. During this procedure, the redundant portion of the LT is excised and the remaining stump of the LT is sutured to the anteromedial hip capsule. To the current authors’ knowledge, these are the only 2 studies that directly incorporated the LT during hip reconstruction, and neither attached the LT back to its anatomical position in the cotyloid fossa.

Temporizing percutaneous fixation has also been reported as a viable strategy in pediatric hip reconstructions. Castañeda et al17 described the use of a smooth K that extends from the acetabulum through the proximal femur and exits the greater trochanter and overlying soft tissue during anterior open hip reduction. Patients were placed in a spica cast postoperatively and pins were left in place for 6 weeks. At final follow-up, they reported 24 redislocations among 621 hips (3.8%) fixed with a transarticular pin. The rate of AVN was reported to be 19.7% (127 of 621), with higher rates seen when the pin was placed in the superior third vs the inferior third of the femoral neck/head. This suggests that if a transarticular pin is used, it should be carefully placed inferiorly, away from the lateral epiphyseal arterial branches. One downside of this treatment approach is that the pin is only temporarily retained.

The technique described in this study provides encouraging results for the use of a suture anchor to reconstruct LT function in the treatment of severely dysplastic hip reconstructions. Given previous histologic data demonstrating the pathologic conversion of the LT in hip dysplasia, it is unclear whether retention of the native pathologic LT provides any long-term benefit. The authors believe that removal of the entire pathologic LT and replacement with a suture anchor allows for concentric reduction, optimal tensioning, and reconstruction of the potential biomechanical contribution of the LT. Ultimately, this technique likely is a temporizing means of stability during the initial postoperative period while the primary stabilizers of hip stability (acetabulum, capsule, soft tissue sleeve) heal. This was evident in several of the authors’ patients, as the femoral head position improved from initial postoperative follow-up. It is unclear how long the suture anchor is functional, although it has been noted in patients with femoral hardware removal, generally at 1 year, that the suture anchor does not appear to be functional.

The rate of AVN was not significantly higher in the current study as compared with previous studies, which reported an AVN rate of 19% to 41%.16–18 Nearly all of the current patients had some degree of radiographic AVN prior to surgery, and only 3 patients (30%) had progression of AVN (patients 3, 6, and 7). All 3 of these cases only progressed by one grade. Placement of the suture anchor through the femoral head and neck occurred through the fovea, located more inferiorly in the head, theoretically causing minimal interruption to the superolateral vessels to the femoral neck.17 Additionally, increased rates of AVN are a well-documented sequela of the anterior open hip reduction, and it is not possible to determine whether the changes in the current cases were a reflection of the surgical approach as opposed to the suture anchoring itself.6,8,12,18

Although 2 cases of redislocation (patients 3 and 6) were reported, the authors believe that this reflects the severity of the patient subset in this case series. In only 1 case of redislocation was a suture anchor previously employed. At the time of revision, the previous anchor was found to be intact. Given this finding, failure was attributed to breakdown at the anchor–suture interface as opposed to failure of the anchor itself. Thus, the authors believe that this example demonstrates an unavoidable complication regarding the described technique. In general, this technique has only been employed in difficult cases with a high anticipated possibility of dislocation or substantial persistent instability after completion of the open reduction and appropriate osteotomies. All of the authors’ patients had neuromuscular, syndromic, or postfemoral lengthening etiologies, all of which portend a worse prognosis.

The authors acknowledge several limitations of this study. Given that the data were collected retrospectively from a small group of patients, predictions regarding the true utility of the proposed technique are limited. Additionally, this study population had a large variety of underlying pathologies, including both idiopathic DDH and syndromic-related severe hip instability. Finally, this study involved a newly proposed technique in a small cohort with a relatively short follow-up, which limits the power of the conclusions.

Conclusion

A previously unreported technique for addressing severe DDH has been presented. The authors believe that this technique may serve as a useful adjunct in severe cases for which traditional open reduction and osteotomy are not sufficient. Additionally, because the long-term effect of leaving a large, nonabsorbable, braided suture across the hip joint is unknown, this technique should be reserved as a salvage procedure for complex, refractory cases. Future studies should aim to expand on this initial investigation and obtain prospective comparative data of the proposed technique.

References

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Demographics and Pre- and Postsurgical Interventions

Patient No.Age, ySexDiagnosisSideTreatment Prior to SurgeryTime From Initial Surgery to RevisionAdditional Deformity?Procedure PerformedAcetabular Osteotomy
121MaleCerebral palsy, chromosomal deletionLF15 moP, F, T, RSATriple
27FemaleDown syndrome, recurrent dislocationsRP, F, C, SATriple
31MaleArthrogryposisRF3 dBilateral congenital vertical talusF, T, C, SA
411FemaleUnidentified syndromeLScoliosis, bilateral genu valgumP, F, C, SATriple
51MaleArthrogryposisRCongenital vertical talusP, F, C, T, SASan Diego
5LAtypical clubfootF, C, T, SA
6a6FemaleCerebral palsyLP, F, C (1st) P, F, SA (2nd)11 moRSA
75MaleChromosomal abnormality of unknown significanceRP, F, T4 yLeg length discrepancyP, F, C, SASan Diego
87FemaleMyelodysplasiaLGenu valgum, dynamic ankle valgusP, T, C, SASan Diego
96FemaleCongenital femoral deficiency, hip dislocation after femoral lengtheningLP, F, T, C1 dFibular hemimeliaF, C, SA

Pre- and Postoperative Radiographic Measurements

Patient No.Preop IHDI GradePostop IHDI GradeFinal IHDI GradePreop AVNFinal AVNPreop AIFinal AIPostop CEA
141231°31°18°
211118°15°35°
3423126°30°
44213351°34°42°
5a4213352°25°
5b4223348°36°
6a4332337°43°25°
74113447°40°32°
84114444°24°32°
94212235°21°35°
Authors

The authors are from the Department of Orthopaedic Surgery (SJM, RWL), Case Western Reserve University, and the Division of Pediatric Orthopaedic Surgery (RWL), Rainbow Babies and Children’s Hospital, Cleveland, Ohio.

The authors have no relevant financial relationships to disclose.

The senior author thanks Dror Paley, MD, for instructing him in the technique described in this study.

Correspondence should be addressed to: Raymond W. Liu, MD, Department of Orthopaedic Surgery, Case Western Reserve University, 11100 Euclid Ave, Cleveland, OH 44106 ( raymond.liu@uhhospitals.org).

Received: March 18, 2019
Accepted: August 22, 2019
Posted Online: August 06, 2020

10.3928/01477447-20200721-08

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