Orthopedics

Feature Article 

Peri-implant Fractures Following Hook Plate Fixation for Unstable Distal Clavicle Fractures

Pei-Lun Ni, MD; Kai-Cheng Lin, MD; Chun-Yu Chen, MD; Yih-Wen Tarng, MD, PhD; Wei-Ning Chang, MD; Jenn-Huei Renn, MD, PhD

Abstract

Clavicle hook plate is a common implant for treating distal clavicle fracture. Although high bone union rate and good functional outcome have been reported, so have several complications, such as osteolysis and fracture of the acromion, loss reduction, hook impingement, and rotator cuff tear. Peri-implant fracture over the medial side of the hook plate is a rare complication. Sporadic cases have been reported, and most of them have had no history of trauma. Between June 2015 and August 2018, 7 patients treated for distal clavicle fracture with a 3.5-mm locking compression hook plate with no history of trauma experienced peri-implant fracture of the medial clavicle. This complication occurred at a mean of 29 days. The incidence rate was 9.8%. Peri-implant fracture following hook plate fixation for distal clavicle fracture was not rare. Small hook angle, prolonged retention of the implant, an eccentric medial screw, high plate screw density, and small clavicle diameter may be risk factors for peri-implant fracture. Regarding treatment, 2 patients chose fracture revision with a distal clavicle locking plate and 5 patients chose conservative treatment. All patients achieved bone union at fracture sites. Surgical and conservative management of peri-implant fracture can achieve good functional outcome. [Orthopedics. 2020;43(5);e359–e363.]

Abstract

Clavicle hook plate is a common implant for treating distal clavicle fracture. Although high bone union rate and good functional outcome have been reported, so have several complications, such as osteolysis and fracture of the acromion, loss reduction, hook impingement, and rotator cuff tear. Peri-implant fracture over the medial side of the hook plate is a rare complication. Sporadic cases have been reported, and most of them have had no history of trauma. Between June 2015 and August 2018, 7 patients treated for distal clavicle fracture with a 3.5-mm locking compression hook plate with no history of trauma experienced peri-implant fracture of the medial clavicle. This complication occurred at a mean of 29 days. The incidence rate was 9.8%. Peri-implant fracture following hook plate fixation for distal clavicle fracture was not rare. Small hook angle, prolonged retention of the implant, an eccentric medial screw, high plate screw density, and small clavicle diameter may be risk factors for peri-implant fracture. Regarding treatment, 2 patients chose fracture revision with a distal clavicle locking plate and 5 patients chose conservative treatment. All patients achieved bone union at fracture sites. Surgical and conservative management of peri-implant fracture can achieve good functional outcome. [Orthopedics. 2020;43(5);e359–e363.]

Distal clavicle fractures account for 12% to 15% of all clavicle fractures,1 with approximately one-fourth being unstable (Neer type II).2 In Neer type II fractures, the distal clavicle fragment is subjected to the distal pull by the weight of the arm and the proximal clavicle fragment is dragged posteriorly by the trapezius muscle. These disturbing forces contribute to fracture displacement and the unstable nature of type II fractures. Various surgical techniques, including Kirschner wire fixation, coracoclavicular fixation with Bosworth screw or dogbone button, Weaver–Dunn procedure, and internal fixation with hook plate, have been reported for distal clavicle fractures.1 With the surgical techniques, the clavicle hook plate is commonly used for unstable distal clavicle fractures because of a high bone union rate with good functional outcome. Nonetheless, several complications, such as delayed union, malunion, nonunion, osteolysis and fracture of the acromion,3 loss reduction (unhooked),4 hook impingement, and rotator cuff tear, have been observed postoperatively.5,6 Peri-implant fracture at the medial side of the hook plate is a rare complication.2,4,7,8 However, there have been sporadic cases, with most of the patients having secondary injury. The current authors report on a series of patients with peri-implant fracture of the medial clavicle without a history of trauma. They discuss the possible risk factors and subsequent management of peri-implant fracture.

Materials and Methods

A retrospective chart review was performed at a single medical center between June 2015 and August 2018. Patients with unstable distal third clavicle fractures treated with a clavicle hook plate (3.5-mm LCP Clavicle Hook Plate; DePuy Synthes, Warsaw, Indiana) were included in this study. The clavicle hook plate is precontoured and made of titanium. It is available with 5 or 6 holes and two hook depths (15 mm and 18 mm). Patients who underwent their initial surgery elsewhere but had their complications managed at the authors' hospital were included in the study. There were 53 patients in the observational cohort; 51 underwent initial treatment at the authors' hospital. Standard shoulder internal/external rotation and clavicular anteroposterior radiographs were obtained at each follow-up visit. The mean follow-up period was 8 months. Patients' demographics (eg, sex, age, and body mass index [BMI]), time between surgery and peri-implant fracture, and mechanism of peri-implant fracture were collected. The authors analyzed the reasons for medial clavicle peri-implant fractures (eg, screw placement configuration, plate position/length, and locking or compression screws in the medial hole of the plate).

Results

Of the 7 patients with peri-implant fractures, 5 underwent initial surgery at the authors' hospital. Thus, the incidence of secondary clavicle fracture following clavicle hook plate fixation was 9.8% (5 of 51). Patient demographics are listed in Table 1. Radiographically, the mean diameter of the clavicle at the fracture side was 0.95 cm (range, 0.91–0.98 cm). The mean interval from surgery to peri-implant fracture was 29 days (range, 22–41 days). A comparison between the patients with peri-implant fracture and the patients without secondary fracture showed no significant difference in terms of age, sex, BMI, locking or compression screw over the medial side, and plate depth or length (Table 2). However, the data revealed that the peri-implant fracture group had a higher female to male ratio and a smaller plate depth. Two cases are presented in detail.

Demographics of Cases of Peri-implant Fracture

Table 1:

Demographics of Cases of Peri-implant Fracture

General Data, Including Implant Features, for the 2 Groups

Table 2:

General Data, Including Implant Features, for the 2 Groups

Case 4

A 55-year-old woman fell when riding a motorcycle and had a left distal clavicle fracture (Neer type IIB). She underwent open reduction and internal fixation with a hook plate. Three weeks after surgery, she experienced sharp pain at the left shoulder after coughing. She presented to the authors' emergency department. A radiograph revealed a peri-implant fracture through the medial screw hole with screw loosening (Figure 1). The patient chose conservative treatment with arm sling protection for the peri-implant fracture. Callous formation was noted on radiograph at 3-month follow-up. After removal of the implant 3 months later, she recovered well and returned to daily activities.

Case 4. Radiograph of internal rotation of the shoulder showing the distal clavicle fracture fixed with a hook plate with a peri-implant fracture over the most medial screw hole (A). Three-dimensional computed tomography scan revealed a fracture from the inferior screw hole to the upper layer of the cortex around the plate and bone junction (B). Axial view computed tomography scan revealed eccentric insertion of the medial screw (C).

Figure 1:

Case 4. Radiograph of internal rotation of the shoulder showing the distal clavicle fracture fixed with a hook plate with a peri-implant fracture over the most medial screw hole (A). Three-dimensional computed tomography scan revealed a fracture from the inferior screw hole to the upper layer of the cortex around the plate and bone junction (B). Axial view computed tomography scan revealed eccentric insertion of the medial screw (C).

Case 6

A 51-year-old man sustained a right distal clavicle fracture in a motorcycle accident. He underwent open reduction and internal fixation with a 6-hole hook plate and cerclage wire at another hospital. Three weeks later, he presented to the authors' clinic with right shoulder pain and a radiographically evident peri-implant fracture through the medial screw hole (Figure 2A). He underwent revision open reduction and internal fixation with a distal clavicle locking plate without bone graft. Bone union was evident at 1-year follow-up (Figure 2B).

Case 6. Anteroposterior radiograph of the distal clavicle fracture fixed with a cerclage wire and clavicle locking plate. In this case, high screw density was found, which can be the cause of peri-implant fracture (A). Anteroposterior radiograph of revision open reduction and internal fixation completed with a precontoured distal clavicle locking plate (B).

Figure 2:

Case 6. Anteroposterior radiograph of the distal clavicle fracture fixed with a cerclage wire and clavicle locking plate. In this case, high screw density was found, which can be the cause of peri-implant fracture (A). Anteroposterior radiograph of revision open reduction and internal fixation completed with a precontoured distal clavicle locking plate (B).

Discussion

Possible Reasons for Peri-implant Fractures From Implants

It has been reported that surgical fixation of an unstable clavicle with a hook plate has a good bone union rate, shoulder functional outcome, and vertical stability.1,9 Other advantages of this implant include easy insertion, efficient maintenance of reduction, and less breakage and migration. Several studies have reported peri-implant fracture of the medial clavicle (Table 3).2,4,7–12 Almost all of these cases were reported to have a secondary injury. To date, there are fewer studies on the risk factors for and management of peri-implant fracture. Hung et al13 and Shih et al14 reported that a smaller hook angle increases the stress on the clavicle, leading to speculation that this is the reason for peri-implant fracture at the medial clavicle. Ramakrishna et al15 and Schuller-Götzburg et al16 reported that the stress-shielding effect and screw micromotion-related bone absorption around the medial screw hole exacerbated the osteoporosis and the stress rises at the medial end of the clavicle. Nadarajah et al8 reported that there is the potential for osteolysis and fracture developing around the implant if it is retained.

Summary of Studies About Peri-implant Fracture

Table 3:

Summary of Studies About Peri-implant Fracture

Possible Reasons for Peri-implant Fractures From Surgical Techniques

Klein et al10 and Flinkkilä et al12 reported that peri-implant fracture of the medial clavicle had an incidence of 4.8% to 13.6%. The current study found a 9.8% incidence of peri-implant fracture, but in the 2 aforementioned studies, all 6 cases involved a fall or high-energy trauma. The trauma mechanism implies that the prolonged retention of the implant exacerbates osteoporosis and leads to fracture through the medial screw hole.7,8,12 However, in the current series, all 7 cases had peri-implant fracture at the early stage of fixation, and osteoporosis related to prolonged retention of the implant could not explain this phenomenon well. Therefore, the authors suggest that controlling errors in technique may prevent peri-implant fracture. First, eccentric positioning of the plate with unicortical purchase will create a new cortical defect, which will lead to a weak point. In the current case 4, 3-dimensional computed tomography revealed that the posterior position of the plate and the eccentric purchase of the medial screw may have increased the stress on the medial end of the screw hole. Second, plate screw density or repeated drilling could increase the risk of peri-implant fracture. Three cases in the current series had 2 screws in the medial combination hole, and 1 case had multiple drilling and a changed plate.

Possible Reasons for Peri-implant Fractures From Patient Factors

Regarding patient factors, bone diameter and acromion anatomy may play important roles. Edgerton et al17 reported that, if the bone defect is greater than 20% of the bone diameter, torque capacity can be decreased to 60%. The average middle third clavicle thickness is 10.5 mm in the Chinese population, and it is significantly less in females.18 In the current case series, the mean diameter of the clavicle at the fracture side was 0.95 cm, making the ratio of the screw hole to bone diameter even greater. In addition, 4 of 5 patients were female, indicating that sex and the diameter of the clavicle may serve as risk factors for peri-implant fracture.

Avoiding This Complication

Bottlang et al19 reported that a non-locking end screw can decrease the fracture risk caused by the locking plate. Hung et al13 and Shih et al14 reported that a large hook angle, a stainless plate, and a longer plate exert less stress on the medial third of the clavicle. However, in the current case series, no significant relationship was found between peri-implant fracture and medial screw choice and plate length. The small number of cases probably affected this result. Deeper implantation of the clavicle hook plate reduces the stress on the clavicle.20 Four of 5 patients with peri-implant fractures had plates of less depth, indicating that hook depth may influence peri-implant fracture. According to previous studies, surgeons may choose a longer and deeper plate to decrease the pressure on the medial clavicle. Surgeons can bend the plate during surgery to fit patient anatomy and thus reduce the incidence of peri-implant fracture.

Managing This Complication

In this case series, 1 of 5 patients underwent re-fixation with a distal clavicle locking plate, and 4 of 5 patients received conservative treatment for the management of peri-implant fracture. All of these patients had bone union at last follow-up. Consistent with other studies, nonoperative treatment was performed because of minimally displaced fracture, absence of symptoms, or good bone union.4,10 If the distal fragment is large enough or displaced, fixation with a plate could lead to good functional outcome.7,8 The current case series revealed that both surgical and nonsurgical treatment will lead to bone union and good functional outcome.

On the basis of the results of these 7 cases of peri-implant fracture, the authors summarized the possible risk factors into 3 groups—patient, surgeon, and implant (Table 4). The authors recommend that a checklist be reviewed before fixing the distal clavicle fracture with a locking hook plate. Before surgery, surgeons must consider the patient's bone quality, diameter, and acromion shape. During surgery, surgeons must check the position of the plate or the presence of excessive torque when placing the plate. Bending the plate or adjusting the hook angle is one way to prevent peri-implant fracture. In managing peri-implant fractures, both surgical and nonsurgical treatment will lead to bone union and good functional outcome.

Summary of Possible Risk Factors for Secondary Fracture and Recommended Solutions

Table 4:

Summary of Possible Risk Factors for Secondary Fracture and Recommended Solutions

Conclusion

Peri-implant fracture following hook plate fixation of distal clavicle fracture was observed in 9.8% of the current cases. An inappropriate surgical technique, including high screw density and plate malposition, may contribute to peri-implant fracture. The management of peri-implant fracture with surgical and conservative treatment could result in good functional outcome.

References

  1. Meda PV, Machani B, Sinopidis C, Braithwaite I, Brownson P, Frostick SP. Clavicular hook plate for lateral end fractures: a prospective study. Injury. 2006;37(3):277–283. doi:10.1016/j.injury.2005.10.017 [CrossRef] PMID:16430895
  2. Zhang L, Xiao H, Gao Y, Zhang H, Zhang L, Tang P. Late function and complications of hook plate implantation for distal-third clavicle fractures: a retrospective study. Acta Orthop Belg. 2017;83(2):304–309. PMID:30399995
  3. Chiang CL, Yang SW, Tsai MY, Kuen-Huang Chen C. Acromion osteolysis and fracture after hook plate fixation for acromioclavicular joint dislocation: a case report. J Shoulder Elbow Surg. 2010;19(4):e13–e15. doi:10.1016/j.jse.2009.12.005 [CrossRef] PMID:20303294
  4. Charity RM, Haidar SG, Ghosh S, Tillu AB. Fixation failure of the clavicular hook plate: a report of three cases. J Orthop Surg (Hong Kong). 2006;14(3):333–335. doi:10.1177/230949900601400320 [CrossRef] PMID:17200540
  5. Lin HY, Wong PK, Ho WP, Chuang TY, Liao YS, Wong CC. Clavicular hook plate may induce subacromial shoulder impingement and rotator cuff lesion: dynamic sonographic evaluation. J Orthop Surg Res. 2014;9(1):6. doi:10.1186/1749-799X-9-6 [CrossRef] PMID:24502688
  6. ElMaraghy AW, Devereaux MW, Ravichandiran K, Agur AM. Subacromial morphometric assessment of the clavicle hook plate. Injury. 2010;41(6):613–619. doi:10.1016/j.injury.2009.12.012 [CrossRef] PMID:20116056
  7. Ding M, Ni J, Hu J, Song D. Rare complication of clavicular hook plate: clavicle fracture at the medial end of the plate. J Shoulder Elbow Surg. 2011;20(7):e18–e20. doi:10.1016/j.jse.2011.06.005 [CrossRef] PMID:21831666
  8. Nadarajah R, Mahaluxmivala J, Amin A, Goodier DW. Clavicular hook-plate: complications of retaining the implant. Injury. 2005;36(5):681–683. doi:10.1016/j.injury.2004.08.010 [CrossRef] PMID:15826633
  9. Erdle B, Izadpanah K, Jaeger M, et al. Comparative analysis of locking plate versus hook plate osteosynthesis of Neer type IIB lateral clavicle fractures. Arch Orthop Trauma Surg. 2017;137(5):651–662. doi:10.1007/s00402-017-2645-7 [CrossRef] PMID:28321570
  10. Klein SM, Badman BL, Keating CJ, Devinney DS, Frankle MA, Mighell MA. Results of surgical treatment for unstable distal clavicular fractures. J Shoulder Elbow Surg. 2010;19(7):1049–1055. doi:10.1016/j.jse.2009.11.056 [CrossRef] PMID:20338788
  11. Obadâ B. Locking or non-locking hook plate in treatment of unstable lateral clavicle fracture. ARS Medica Tomitana. 2014;20:150–152.
  12. Flinkkilä T, Ristiniemi J, Lakovaara M, Hyvönen P, Leppilahti J. Hook-plate fixation of unstable lateral clavicle fractures: a report on 63 patients. Acta Orthop. 2006;77(4):644–649. doi:10.1080/17453670610012737 [CrossRef] PMID:16929443
  13. Hung LK, Su KC, Lu WH, Lee CH. Biomechanical analysis of clavicle hook plate implantation with different hook angles in the acromioclavicular joint. Int Orthop. 2017;41(8):1663–1669. doi:10.1007/s00264-016-3384-z [CrossRef] PMID:28097386
  14. Shih CM, Huang KC, Pan CC, Lee CH, Su KC. Biomechanical analysis of acromioclavicular joint dislocation treated with clavicle hook plates in different lengths. Int Orthop. 2015;39(11):2239–2244. doi:10.1007/s00264-015-2890-8 [CrossRef] PMID:26183142
  15. Ramakrishna K, Sridhar I, Sivashanker S, Khong KS, Ghista DN. Design of fracture fixation plate for necessary and sufficient bone stress shielding. JSME Int J. 2004;47(4):1086–1094. doi:10.1299/jsmec.47.1086 [CrossRef]
  16. Schuller-Götzburg P, Krenkel C, Reiter TJ, Plenk H Jr, . 2D-finite element analyses and histomorphology of lag screws with and without a biconcave washer. J Biomech. 1999;32(5):511–520. doi:10.1016/S0021-9290(98)00156-0 [CrossRef] PMID:10327005
  17. Edgerton BC, An KN, Morrey BF. Torsional strength reduction due to cortical defects in bone. J Orthop Res. 1990;8(6):851–855. doi:10.1002/jor.1100080610 [CrossRef] PMID:2213342
  18. Qiu XS, Wang XB, Zhang Y, Zhu YC, Guo X, Chen YX. Anatomical study of the clavicles in a Chinese population. BioMed Res Int. 2016;2016:6219761. doi:10.1155/2016/6219761 [CrossRef] PMID:27088088
  19. Bottlang M, Doornink J, Byrd GD, Fitzpatrick DC, Madey SM. A nonlocking end screw can decrease fracture risk caused by locked plating in the osteoporotic diaphysis. J Bone Joint Surg Am. 2009;91(3):620–627. doi:10.2106/JBJS.H.00408 [CrossRef] PMID:19255222
  20. Lee CH, Shih CM, Huang KC, Chen KH, Hung LK, Su KC. Biomechanical analysis of implanted clavicle hook plates with different implant depths and materials in the acromioclavicular joint: a finite element analysis study. Artif Organs. 2016;40(11):1062–1070. doi:10.1111/aor.12679 [CrossRef] PMID:26814438

Demographics of Cases of Peri-implant Fracture

Case No.Age, y/SexInterval From Fixation to New Fracture, dMedial Combination HoleTreatment
158/F22LRevision with LCP
251/F23C+LConservative
324/F41CConservative
455/F39CConservative
550/M34L (multiple drill)Conservative
6a51/M22C+LRevision with LCP
7a63/F22C+LConservative

General Data, Including Implant Features, for the 2 Groups

FactorPeri-implant Fracture (n=5)No Peri-implant Fracture (n=46)P
Sex, No.
  Female426.31a
  Male120
Age, mean, y46.8043.11.59b
Body mass index, mean, kg/m223.3623.26.67b
Medial screw, No.
  Compression333.58a
  Locking213
Holes, No..95a
  5219
  6327
Depth, mm, No.
  15428.40a
  18118

Summary of Studies About Peri-implant Fracture

Study (Year)No./Total No. of CasesType of Hook PlateTraumaTime IntervalaManagement
Nadarajah et al8 (2005)1SynthesYes1 y1 plate
Charity et al4 (2006)1/23SynthesYes1 mo1 conservative
Ding et al7 (2011)1Yes40 d1 plate
Flinkkilä et al12 (2006)3/63Synthes (Stratec)Yes2 conservative 1 plate
Klein et al10 (2010)3/22SynthesYes3 conservative
Obadâ11 (2014)2/48
Erdle et al9 (2017)1/19No6 wk1 hook plate
Zhang et al2 (2017)1/61SynthesYes42 mo1 plate

Summary of Possible Risk Factors for Secondary Fracture and Recommended Solutions

Factor TypeRisk FactorRecommended Solution
Patient relatedSmall diameter of clavicle17Sharp acromion slope Osteoporosis8Combine coracoclavicular stabilization procedure Adjust hook depth and angle Clavicle inlet view for bone diameter
Surgeon relatedInappropriate plate position Retaining the implant9High plate screw densityPlace plate at center of bone Remove plate as soon as bone healing Appropriate screw density
Implant relatedStress-shielding effect8Small hook depth and angle13Titanium alloy14Bend the plate to maximize contact area (more length, large angle and depth)
Authors

The authors are from the Department of Orthopaedics, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan.

The authors have no relevant financial relationships to disclose.

Correspondence should be addressed to: Kai-Cheng Lin, MD, Department of Orthopaedics, Kaohsiung Veterans General Hospital, 386 Ta-Chung 1st Rd, Kaohsiung, Taiwan ( orthokcl@gmail.com).

Received: December 26, 2018
Accepted: May 20, 2019
Posted Online: July 07, 2020

10.3928/01477447-20200619-01

Sign up to receive

Journal E-contents