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Corresponding author. Department of Orthopedic Surgery, University of Minnesota, 2450 Riverside Avenue South Suite R 200, Minneapolis, MN 55454, USA. Tel.: 612-273-1177.
Tibial tubercle osteotomy (TTO) is a common procedure that is frequently used in the treatment of recurrent patellar instability and/or patellar chondrosis. Current estimates of TTO complications in the literature vary widely, with complication rates reaching 59 percent. This variability is due, in part, to inconsistent definitions of complication between studies. The purpose of this study was to identify our complication rate following TTO procedures, with sub-analysis of whether the complication rate was affected by:
1. An intra-articular component defined as an additional procedure that altered post-operative rehabilitation and
2. A distalization of the tubercle translation.
Methods
All patients between May 2009 and May 2015 who underwent a TTO were retrospectively identified. Complications were defined as major (fracture of the tibia, deep infection, non-union, delayed union, arthrofibrosis, deep vein thrombosis (DVT) and loss of screw fixation) versus minor (superficial wound infection, disturbance of cutaneous sensation and delay in wound healing). Subgroup analysis of distalization versus no distalization and intra-versus extra-articular concomitant procedures were also analysed.
Results
One hundred and sixty-three TTOs in 150 patients were included in the final cohort with a mean follow-up of 21.3 months. The overall complication rate was 35 major complications (21.5%) and 13 minor complications (8.0%), with a total complication rate of 29.5 percent. TTO distalization did not increase the rate of complications. DVT was only seen in the intra-articular procedure cohort (n = 3/1.8%). Arthrofibrosis was the most common complication, occurring in 17 knees.
Conclusion
The overall complication rate of TTOs was 29.5%, with arthrofibrosis (10.4%) as the largest complication. DVT increased with concomitant intra-articular procedure. Distalization of the tubercle compared to no distalization had no significant effect on complications.
]. TTOs require transferring the tubercle medially, distally, anteriorly or a combination of these directions guided by the patient's symptoms and osseous anatomy [
]. TTOs frequently medialise the tubercle to decrease the lateral vector of the distal extensor mechanism. This is indicated in cases of localised cartilage wear on the lateral and/or inferior patella, and in some cases, to protect cartilage restoration procedures of the PF joint. Tubercle fragment distalization corrects patella alta. TTOs performed for patellar instability are frequently combined with patellar stabilisation procedures, such as medial patellofemoral ligament (MPFL) reconstruction, medial retinacular imbrication, lateral retinacular release/lengthening and trochleoplasty [
Until recently, literature described a range of TTO complication rates between 0 and 12% though these studies were limited by their cohort sizes 116 knees) [
Elmslie-Trillat, Maquet, Fulkerson, Roux Goldthwait, and other distal realignment procedures for the management of patellar dislocation: systematic review and quantitative synthesis of the literature.
One recent retrospective cohort study describes a TTO complication rate of 58% (n = 88) out of 153 TTOs, including a 21% (n = 32) painful hardware removal rate [
]. This high complication rate is influenced by their inclusion of painful hardware removal as a complication, not classified as a complication in most publications. Additionally, the concomitant procedures reported in this study are MPFL reconstruction and lateral retinacular release, with no mention of additional bony procedures. One study performed TTOs with concomitant patellar tendon tenodesis and reports a total complication rate of 14.8% with a mean follow-up of 9.6 years [
]. Moreover, a 2017 systematic review examined 21 TTO outcomes studies (1055 knees) and found a complication rate of 8% (79 complications), with an additional 21% (219 knees) requiring reoperation (170 of which removed painful hardware) [
TTO complications can be classified as major and minor. Major complications reported in the literature are deep vein thrombosis (DVT), tibia fracture, nonunion, temporary common peroneal neuropraxia, deep infection requiring surgical debridement, arthrofibrosis requiring surgery and subsequent patellar instability [
Elmslie-Trillat, Maquet, Fulkerson, Roux Goldthwait, and other distal realignment procedures for the management of patellar dislocation: systematic review and quantitative synthesis of the literature.
The purpose of the present study is to identify the complication rate resulting from tibial tubercle osteotomies, with sub-analysis of whether the complication rate was affected by:
1.
An intra-articular component defined as an additional procedure that altered post-operative rehabilitation and
2.
A distalization of the tubercle translation.
Methods
After Institutional Review Board (IRB) approval was obtained (University of Minnesota IRB #1609M94383), this study was determined to be exempt from further review under federal guidelines 45 Code of Federal Regulations Part 46.101(b) category 2: Surveys and interviews. All ethical standards of maintaining patient confidentiality have been employed, including those in accordance with the United States Health Insurance Portability and Accountability Act. A retrospective chart review was performed on 177 TTOs. One hundred and sixty-three knees were included in the final study cohort (Table 1). Three months were chosen as the minimum follow-up as the majority of complications have declared themselves by that time. All TTOs were performed from May 2009 to May 2015 by four fellowship trained orthopaedic surgeons. Surgical technique is elsewhere described [
Demographics were collected on all patients and included age at operation, gender, body mass index and tobacco use (Table 2). Tobacco pack per day, smoking history and date of smoking cessation were noted in cases in which the data were available.
Major complications were tibia fractures (Fig. 1), deep infection requiring surgical debridement, arthrofibrosis defined as knee stiffness requiring surgical intervention, DVT, loss of tibial tubercle fixation (broken screw) with subsequent healing, non-union and delayed union. For the purposes of data collection, the definition of non-union (Fig. 2) was the absence of bony union necessitating a refixation procedure. Delayed union was defined as delayed bony union after 3 months which resolved with non-operative management.
Fig. 1Sagittal view of the tibia with a fracture emanating from the anterior cortex of the tibia, at the distal aspect of the osteotomy bone segment. Interval healing is present.
Fig. 2Sagittal view of the tibia four months after surgical distalization tibial tubercle osteotomy. The bent distal screw, migration of the osteotomy block and the wide gap between osseous surfaces indicate a non-union.
Minor complications included wound dehiscence treated non-operatively, superficial infection and loss or decrease of cutaneous sensation. Surgeons evaluating patients post-operatively were not blinded to details regarding the procedure. Data were also collected regarding previous, concomitant and subsequent procedures pertinent to the operative knee.
For the purposes of this study, we sub-classified intra-articular procedures as any intra-articular bony procedure that changed the TTO post-operative protocol in regards to limited motion and/or weight bearing status.
The post-operative protocol employed requires partial weight bearing in a locked knee immobilizer for four weeks, opening the brace when sitting and for exercises. At four weeks, the protocol is advanced to weight bearing as tolerated depending on patient- and imaging- related factors. This TTO protocol is attached as an appendix. Concomitant intra-articular procedures (49 knees) included cartilage restoration such as autologous chondrocyte implantation (ACI) and osteochondral allograft (OCA) transplantation (n = 31/63%), microfracture (n = 13/27%) and/or trochleoplasty (n = 5/10%). Concomitant extra-articular procedures (114 knees) were largely patellar stabilisation including MPFL reconstruction with or without lateral retinaculum release/lengthening (n = 82/72%), lateral retinaculum release/lengthening (n = 20/18%) and other soft tissue patellar stabilisation (n = 12/10%). When a patient had both concomitant intra- and extra-articular procedures, they were placed in the intra-articular subgroup.
Statistical analysis
All variables were evaluated by Chi-square analysis to determine statistical significance between cohorts. Level of significance was set at P < 0.05.
Results
The final study cohort represents 163 knees in 150 patients, with a mean follow-up of 21.3 months (range: 3 months to 6.8 years). The minimum follow-up was 3 months. Ninety percent had at least 6 months of follow-up. Fourteen patients were excluded due to lack of sufficient follow-up; no complications were recorded in the excluded patients. Ninety-one of 163 TTOs (55.8%) had a primary diagnosis of patellar instability and 32 knees (19.6%) had a primary diagnosis of PF chondral damage. Forty knees (24.5%) carried a combined diagnosis of patellar instability and cartilage wear.
The overall complication rate was 29.5%, the major complication rate was 21.5% and the minor complication rate was 8.0% (Table 3). The most common complication was arthrofibrosis in seventeen knees (10.4%).
Table 3Tibial tubercle osteotomy complication rates: intra- versus extra-articular procedure.
Out of those with arthrofibrosis in the intra-articular subgroup (n = 5), one patient developed ‘catching’ in the operative knee and required further surgery. Of those with arthrofibrosis in the extra-articular subgroup (n = 12), one patient had a non-union following treatment for arthrofibrosis resulting in reoperation with bone grafting. Fifteen out of seventeen arthrofibrosis cases achieved functional motion, comparable to the other side.
For the sub-analysis, there were no significant differences between the overall complication rate of TTOs with or without concomitant intra-articular procedure. Of the 49 osteotomies that underwent a concomitant intra-articular procedure, there were 12 complications (24.5%) in 9 knees. Of the 114 osteotomies with a concomitant extra-articular procedure, there were 36 complications (31.6%) in 27 knees (Table 3).
The rate of DVT was very low (n = 3/1.8%) and was present only in the intra-articular procedure cohort (p = 0.03, Table 3). None of the DVTs had a subsequent pulmonary embolism; all were treated with greater than or equal to three months of anticoagulation.
In the sub-analysis between distalized and non-distalized subgroups, there were no significant differences in overall complication rates (p = 0.39, Table 4).
Table 4Complications following distalization versus no distalization.
When total bony complication rates (delayed union, non-union (Fig. 2), tibia fracture (Fig. 1) and loss of screw fixation) were grouped, complication rates did not differ significantly when comparing intra- (n = 3, 6.1%) versus extra-articular (n = 12, 10.5%) subgroups (p = 0.56, Table 3) or between distalization (n = 10, 10.3%) versus no distalization (n = 5, 7.6%) subgroups (p = 0.60, Table 4). There were 2 delayed unions; both healed with the use of a bone stimulator. All non-unions required reoperation with bone grafting (n = 1) or revision fixation (n = 3); all were healed by last follow-up.
There were no predictors of complications in our demographic variables (body mass index/age/gender; Table 2). Notably, previous surgery and smoking status (prior or current) was not associated with an increased rate of complication, though this sub-grouping was too small to make meaningful comparisons. Seventy-eight percent of our cohort were ‘never smokers’. It is the current practice of the authors to require smoking cessation prior to proceeding with TTO surgery.
Elective hardware removal was completed in 19 knees (11.7%). The majority of screws used in our patients were 3.5 mm in diameter.
Discussion
The most important finding of this study is the complication rate of TTOs is high (29.5%), most of them being major complications. Arthrofibrosis was the most common complication (10.4%) and affected patients regardless of TTO distalization or a concomitant intra-articular procedure.
Past literature reports TTO arthrofibrosis rates of up to 2.8 percent [
]. One recent study reports an arthrofibrosis rate of 22%, though all patients in this study underwent concomitant cartilage restoration procedures such as ACI or OCA [
]. In another recent study of a cohort undergoing distalization TTO with no secondary intra-articular procedures, the rate of arthrofibrosis (8.8%) was associated with the length of the distalization [
]. In our study, we compare the complications of TTO paired with intra-articular (includes ACI, OCA, microfracture and trochleoplasty) versus TTO with associated soft tissue extra-articular procedures and no concomitant bony procedures. No significant difference in rate of arthrofibrosis was found between these groups.
The rate of arthrofibrosis requiring surgical intervention is high in the present study and may indicate the importance of adherence to post-operative physical therapy and early mobility following TTO, despite concomitant procedures. Adequate pain control and rigid fixation are additional strategies that support early motion.
All three DVT in this study were in the intra-articular subgroup (Table 3), resulting in a significant difference compared to the extra-articular subgroup. This finding may be the result of a possible longer operating time with the addition of an intra-articular procedure. Each patient should receive an individualised and risk stratified decision regarding DVT prophylaxis.
One purpose of our study was to see if distalization was an independent risk factor for having a complication given the potential higher forces experienced at the site of the tubercle following distalization, the loss of a periosteal hinge and with the inferior osteotomy site being closer to diaphyseal bone. Our data did not support this hypothesis (Table 4). The rate of complication in the distalization group did not differ significantly from the non-distalized group (p = 0.39), though one publication reports significantly increased rates of delayed union among TTOs that are distalized [
]. Post-operative management, specifically time on crutches and progression to full weight-bearing, likely plays a role in this variable; granularity of post-operative management could not be ascertained from the current and past literature. Our post-operative protocol is conservative, in that we keep the patient partial weight-bearing until radiographic evidence of complete or near complete union is demonstrated with pain-free ambulation.
The rate of hardware removal in our study (11.7%) represents a lower rate than the current literature, which reports a symptomatic hardware removal rate of up to 59 percent [
]. If the present study had a greater average time to final follow-up, we may have detected a higher hardware removal rate. Additionally, the current literature shows that a screw size of 4.5 mm is associated with a higher rate of post-operative discomfort and subsequent hardware removal when compared to the predominant screw size used in our patient population (3.5 mm) [
] lower than the present study. The literature's definition of neurologic complications includes both saphenous neuromas and temporary peroneal nerve palsies, while our study focused on superficial nerve paraesthesia and dysesthesias from the infrapatellar branch of the saphenous nerve. No neurologic motor dysfunction specific to the peroneal nerve was recorded in our study. This differed from prior literature's definition of neurologic deficit and may account for the variability found between values in the literature and this present study.
The uniqueness of this study is the evaluation of post-operative TTO complications between concomitant intra- versus extra-articular procedures and between TTO with and without distalization. This data may better inform the patient-physician conversation surrounding this operation and its risks, especially when additional intra-articular procedures are performed with the TTO.
Limitations
Limitations of the study include the retrospective design. However, this is somewhat offset by the sample size as well as a 90% follow-up rate at 6 months. Additional limitations include the heterogeneity of concomitant procedures and variations in the degree of tibial tubercle translation, both of which may result in a heterogeneous population and may negatively impact the power of our study. A description of indications for each procedure is not within the scope of this paper and therefore not included.
Conclusion
TTOs are associated with a high rate of complications. Arthrofibrosis was the most highly reported complication in our study. DVT was the only complication significantly affected by concomitant intra-articular procedures. There were no significant differences when comparing complications of distalized and non-distalized subgroups. This study provides insight into the rate and types of complications associated with TTO procedures.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Appendix A. Supplementary data
The following is the Supplementary data to this article:
Elmslie-Trillat, Maquet, Fulkerson, Roux Goldthwait, and other distal realignment procedures for the management of patellar dislocation: systematic review and quantitative synthesis of the literature.
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