Reconstruction of the Medial Patellofemoral Ligament with Patellar Transosseous Sutures: Cross-Sectional Study with 34 patients

Keywords

medial patellofemoral ligament - reconstruction - patellar instability

Introduction

Different structures are responsible for patellar stabilization, including muscular, ligament and osseous factors. Among them, the medial patellofemoral complex has a significant role. The main medial stabilizer of this complex is the medial patellofemoral ligament (MPFL). Biomechanical studies show that it contributes between 50% and 80% to the medial contention of the patella, and it varies depending on the degree of knee flexion.[1] [2] [3]

A common finding in acute dislocations of the patella is MPFL tear; it is a major contributing factor for recurrent patellar instability that can lead to worse functional outcomes and possibly osteoarthritis in the long term.[1] [4] [5] [6] [7] Patellar dislocation is more frequent in young individuals, women, and patients who have suffered a previous dislocation. The risk of redislocation is of 17% after the first episode, and of 50% after the second, with high variability according to the presence of associated factors.[2] [8] [9] [10]

Anatomical factors like trochlear dysplasia, high positioned patella, lateralization of the tibial tuberosity, and patellar tilt are considered major risk factors for recurrence.[11] The first episode of luxation is commonly treated conservatively, but, in recurrent dislocations, surgical treatment is recommended.[12] Medial patellofemoral reconstruction (MPFLR) is probably the most widely used surgical technique.[13] [14] [15]

A great variety of techniques have been described for medial patellofemoral reconstruction, but none of them could actually be considered a gold standard.[8] Techniques differ regarding types of graft, fixation system, presence of tunnels, tensioning, and use of implants or devices. Different choices of grafts have been described, but no authors have reported significant advantages from the rest.[13] Hamstring autograft is probably the most commonly used for MPFL reconstruction.[12] Common patellar fixation techniques for MPFLR include anchors, bone tunnels, and interference screws.[16] [17] [18] [19] Studies comparing fixation methods show a higher risk of patellar fracture in bone tunnel techniques.[17] [20] [21] [22] [23] [24] [25] Transosseous sutures have been described also for MPFLR with single-bundle reconstruction,[26] but no clinical studies were found for double-bundle reconstruction.

The aim of the present study is to evaluate double-bundle MPFL reconstructions in patients with recurrent lateral patellar dislocation operated with a novel patellar graft fixation technique using transosseous sutures. The primary objective is to determine the redislocation rate and functional outcomes, including return to sports, and the secondary outcomes include an assessment of risk factors, associated injuries, and complications.

Methods

We designed an observational cross-sectional study including patients who underwent MPFLR with patellar transosseous sutures between 2013 and 2019. The inclusion criteria were the following: patients with recurrent lateral patellar dislocation, primary reconstruction surgery, use of hamstring autograft, patellar fixation with transosseous sutures, minimum of 12 months for the evaluation, and surgery performed by the same first surgeon. The data obtained from clinical records and procedure protocols includes age, date of injury, date of surgery, relevant clinical evaluation at presentation and final follow-up, presence of risk factors, associated injuries, and meniscal and chondral status of the knee. Data regarding the postoperative Kujala Score and return to sports was obtained prospectively through a questionnaire.[27] [28]

The standard preoperative evaluation included standard X-rays, computed tomography (CT) and magnetic resonance imaging. Anatomical risk factors were recorded using the Caton index in X-rays for patellar height, the Dejour classification for the degree of dysplasia,[29] the distance between the tibial tubercle and the trochlear groove (TT-TG) in the CT for tibial tubercle lateralization, and the hip-to-knee angle for femoral rotation.

All patients were operated on with a standarized surgical technique. The patient is placed in supine position on the operating table. Standard arthroscopy equipment and intraoperative radioscopic image intensifier are used in all cases. First, an examination under anesthesia to assess patellar laxity, with the lateral displacement test measured in quadrant in full extension, with 30° and 60° of knee flexion. Then, arthroscopic standard portals to asses MPFL status, patellar chondral injuries, patellofemoral dynamic tracking, and detection and treatment of associated injuries, such as meniscal or chondral lesions and loose bodies. Harvesting of an autograft from the gracilis tendon is performed in a minimally-invasive manner, by a 2-cm incision over the medial portion of the posterior flex fold of the knee in 90° of flexion and hip abduction, with the use of open tendon stripper first to retrieve the proximal portion in a retrograde manner, and then a closed tendon stripper for the distal part of the tendon in a anterograde manner. In patients in which a tibial tubercle osteotomy is planned as an associated procedure, the gracilis tendon is harvested in a retrograde fashion as commonly used, through the incision of the osteotomy approach.

Next, we approach the patella with a longitudinal surgical incision over the proximal medial border. The incision is deepened to the bone with electrocautery, always extra-articularly, creating a bony bed that goes from the midpoint to the most proximal part of the medial border of the patella ([Figure 1A]). Subsequently, with a 1.5-mm drill, 2 oblique perforations are performed between the deeper (posterior) rim of the bony bed and the anterior surface of the patella with a 45° inclination, serving as passage to the sutures ([Figure 1B]). Once passed through bone, the sutures are returned under the periosteum to finally exit at the superficial (anterior) rim of the bony bed previously described. The procedure is repeated 2 cm to 3 cm apart. Hence, two anchoring points are now available to fixate the graft in the middle and proximal medial aspects of the patella with high resistance, non-absorbable sutures ([Figure 1C]).

Fig. 1 (A) Preparation of the bony bed on the medial side of the patella. (B) Axial X-ray of the patella with schematic drawing of oblique perforation at 45° and the subperiosteal passage of high-resistance sutures serving as an anchoring point on the bony bed (white arrow), (C) Gracilis autograft placed on the bony bed fixated with high-resistance sutures (light blue sutures) to the medial aspect of the patella through both anchoring points (black arrows). (D) Graft fixated on the patella ready to check the isometry of the femoral fixation.

Once the graft is fixated to the patella, both loose ends are pointed to the femoral site of fixation and sutured together, taking care to keep the same tension in both reins. The femoral attachment site is addressed through a transverse skin incision and located by palpation in the flat spot between the medial epicondyle and adductor tubercle. This point is double-checked under intraoperative X-Ray at the anatomical point described by Schöttle et al.,[30] taking special care to obtain a true lateral view; additionally, we assess its functionality, testing the correct isometricity, detecting the tension of the graft in flexion and extension, with the correct point detected by the higher degree of tension in full extension. In that point, we place a 2,5-mm guide that is overdrilled with a 7-mm tunnel of 40 mm in length ([Figure 1D]).[30] The graft is passed between layers 2 (vastus medialis) and 3 (capsule) of the medial patellofemoral ligament complex and fixated with a 7 mm x 28 mm interference screw to the femur, with the knee at approximately 30° of flexion, and keeping manual positioning of the patella to avoid overtensioning. In cases of open physis, femoral fixation was performed with sutures around the insertion of the distal adductor tendon.

An additional surgery was indicated for the management of associated risk factors in cases with significant abnormal patellar height or lateralization of the tibial tubercle. The degrees of dysplasia and femoral rotation did not change the protocol. A tibial osteotomy was performed with medialization of the tibial tubercle in patients with TT-TG longer than 20 mm and/or distalization of the tibial tubercle in cases with a Caton index of 1.4 or higher. When distalization osteotomies were indicated, associated medialization was added only if the TT-TG was longer than 24 mm, because of the intrinsic “medializing effect” of distalization. In cases if open physis, isolated MPFLR was performed regardless of osseous abnormalities in order to avoid growth disturbances.

A statistical analysis was performed with the Chi-squared and exact Fisher tests for the parametric variables. The Mood median or Mann-Whitney tests were used for the non-parametric variables. The normal distribution of different variables was tested with the Anderson-Darling or Kolmogorov-Smirnov tests. The median was used to determine differences in the case of variables that did not have normal distribution. The confidence interval (CI) of the proportions was calculated using the exact method for proportions. Statistical significance was set as p-values lower than 5%.

Results

The present study initially included 44 patients who met the criteria, but 10 patients could not be reached at the final evaluation; thus, a total of 34 patients were finally included.

In this group of 34 patients, the mean age was 22.8 years at the time of surgery (range: 10 to 42 years; standard deviation [SD]: 9.1; median: 20 years). Regarding gender, 50% (17 cases) were male and 17 cases were female patients.

Participation in sports was observed among 94% of the patients, and it is summarized in [Table 1]. The clinical evaluation of these patients showed generalized ligamentous hyperlaxity in 8 (24%), genu valgus in 14 (42%), and presence of significant clinical J sign in 2 (6%). According to the anatomical factors studied in our protocol, trochlear dysplasia was the most common finding, in 30 cases (88%). The degree of dysplasia according to the Dejour classification system is presented in [Table 2]. Patella alta according to Caton index > 1.2 was found in 8 patients (24%), with 2 (6%) of them with an index of 1.4. No patients had a Caton index > 1.4.

Table 1

Variable	Results
Soccer	15
Gym	5
Basketball	5
Cycling	4
More than 1 sport	8
Other sports:	12
Volleyball, skating, pole dance, dancing, cheerleading, cross-fit, kick-boxing, jogging, squash, walking, and weightlifting
No physical activity	2

Table 2

Variable	Results
Dysplasia:	30 (88%)
Dejour A	16
Dejour B	9
Dejour C	4
Dejour D	1
No dysplasia	4 (12%)

Abnormal lateralization of the tibial tubercle according to the TT-TG (> 15 mm) was found in 24 patients (71%). Of these patients, 11 had > 20 mm, and were considered for surgical correction by medialization osteotomy of the tibial tubercle. In total 4 patients in this group had open physis which contraindicated the procedure, so osteotomy was performed in the remaining 7 patients. Of these 7 patients, 2 had a concomitant Caton index of 1.4, so the osteotomy was performed with a distalizating and medializating effect in both of them. ([Table 3])

Table 3

Gender	Age	TTTG	Caton index	Dysplasia*	Associated TTO
Female	14	24 mm	1.2	A	No (open physis)
Female	13	22 mm	1.1	A	No (open physis)
Male	14	25 mm	1.3	A	No (open physis)
Male	35	21 mm	1.1	A	No (open physis)
Female	20	23 mm	1.1	C	Medializing
Female	20	22 mm	1.1	C	Medializing
Female	27	23 mm	1.1	A	Medializing
Female	17	23 mm	1.2	B	Medializing
Male	39	23 mm	1.2	C	Medializing
Male	15	25 mm	1.4	B	Medial + distalizing
Male	15	24 mm	1.4	C	Medial + distalizing

During the initial arthroscopy, a routine systematic examination of the entire joint in search for associated injuries and loose bodies showed a high prevalence of chondral injuries, significantly more frequent in the patella (31 cases, 91%) Only minor lesions were found in the meniscus, which required no treatment, and 12 patients (35%) had loose bodies that were removed ([Table 4]).

Table 4

Variable	Results
Meniscal injuries	7 (21%)
Chondral injuries:
Medial tibiofemoral	0
Lateral tibiofemoral	5 (15%)
Patellofemoral:	32 (94%)
No injury	2 (6%)
Isolated trochlear	1 (3%)
Isolated patellar	25 (73%)
Both	6 (18%)
Loose Body	12 (35%)

The mean time elapsed between the first dislocation and surgery was of 72 months (range: 1 to 328 months; SD: 85.4; median: 39.7). The final evaluation with questionnaire or survey after surgery had a mean follow-up of 30.4 months (SD: 14.6) with a range between 12 and 72 months.

Regarding the functional results, the mean Kujala acore was of 89.4 points (SD: 12.8), with a median of 93.5 points, and a range between 51 and 100 points. There were no cases of postoperative dislocation during the survey and the clinical follow-up. No revision surgery was recorded. Only 2 (6%) patients complained of postoperative pain or mild instability during sports or daily activities. No other complications were identified during the follow-up.

Regarding the rate of return to sports, of the patients who participated in sports preoperatively (32/34 patients), 81% (26 patients) returned to sports after MPFL reconstruction, and 47% (15 cases) returned to their previous level of participation. The mean time until the return to sports was of 8.8 months (SD: 5.5), with a median 6.5, and a range between 2 and 24 months.

We compared 2 different groups according to our treatment protocol regarding the indication for an associated tibial tubercle osteotomy: one treated with isolated MPFLR (27 patients) and the other with MPFLR associated to an osteotomy (7 patients). When comparing these two groups, we found no differences regarding the Kujala score, the dislocation rate, and the return to sports rate, as seen on [Table 5].

Table 5

Group	Redislocation rate	Median Kujala	Mean Kujala	Rate of return to sports
Isolated MPFLR	0%	93 (CI: 89.9–95)	88 (CI: 82.7–93.6)	78% (CI: 58%–91%)
MPFLR + associated TTO	0%	96 (CI: 88.6–100)	94 (CI: 89.1–99.4)	71% (CI: 29%–96%)
p-value	Not available	0.671	0.083	0.736

Discussion

The main goals of the present study were to assess the functional outcomes and redislocation rates. Regarding the evaluation of the functional results, the Kujala score is one of the most common scores used in patellofemoral disorders.[1] [28] Schneider et al.,[31] in their systematic review, found a pooled estimate between 81.6 and 90 points using the Kujala score. In addition to this, they estimated the risk of objective recurrent instability after surgery between 0.3% and 2.1%.[31] In [Appendix 1], we summarized the comparative findings in different clinical studies that involved more than 30 patients mostly from two major systematic reviews.[1] [47] The redislocation rates among them vary between 0% and 4.5%, and the Kujala scores, between 75 and 94, which is comparable to the findings in the present series.

Appendix 1

Study	N° of patients	Mean follow-up (months)	Graft type	Kujala score (standard deviation)*	Redislocation
Howells et al., 2012y	193	16	ST	81.7	0
Astur et al., 2015d	58	60	GC	79.6 (14.5)	0
Goyal et al., 2013d	32	38	QD	91.3	0
Kang et al., 2014d	45	34	ST	90.9 (6.6)	0
Kita et al., 2015d	42	38	ST	93.6	4.5%
Krishna Kumar et al., 2014d	30	25	GC	87	0
Lee et al., 2017d	44	48	GC/synthetic	83 (16)	0
Mulliez et al., 2015d	124	12	GC/ST	74.7 (20.5)	0.8%
Niu et al., 2017d	64	25	ST	91.8 (3.7)	0
Niu et al., 2017d	32	48	ST	92 (4.8)	0
Panni et al., 2011d	51	33	ST	86.8 (14.4)	0
Valkering et al., 2017d	31	37	GC	80.9 (2)	0
Von Engelhar et al., 2018d	30	24	GC	92 (10)	0
Wagner et al., 2013d	50	12-24	GC	87 (13)	2%
Han et al., 2011y	52	68	ST	82.6	0
Lippacher et al., 2014y	68	25	GC	87.5	2%
Ma et al., 2013y	32	40	ST	87	0
Matsushita et al., 2014y	34	108	ST	92	0
Panni et al., 2011y	48	33	ST	86.8 (7.2)	0
Smith et al., 2014y	30	12	ST/GC	84.1 (20.6)	1%
Wang et al., 2013y	58	48	ST	92.9 (4.32)	0
Zhou et al., 2014y	32	18	ST	91 (7)	0
Present study	34	30	GC	89.4 (12.8)	0

In the present series, the mean Kujala score was of 89.4 points, and no dislocation episodes (0%) were found in a mean follow-up of 30 months.

Achieving adequate patellar stabilization with satisfactory functional results is probably the main goal of our surgery, but return to sports is of crucial importance when considering our results and the expectations of the patients, especially those young and active. Nevertheless, few studies report their return to sports rate as shown by Schneider et al.[31] They report a pooled estimate of the rate of return to sport of 84% (CI: 71% to 97%), which comparable to the 81% found in the present study. When considering patients that return to their previous level of participation, the results are significantly lower; Matassi et al.[32] and Lippacher et al.[19] report 39% and 53% respectively. Nevertheless, with a longer follow-up (6 years), Ambrožič qnd Novak[33] report a 70% return to the previous level. Many studies[34] [35] addressing this issue show a slow recovery with prolonged programs of rehabilitation (> 8 months) after MPFLR. There are reports of even slower recovery if a tibial osteotomy is associated.[19] It has been demonstrated that subtle deficits in the global evaluation may remain for long time after the full discharge to return to sports.[36]

The MPFLR techniques have shown many differences among clinical studies. The type of patellar fixation is probably one the most significant, with a great variety that makes them difficult for comparison.

In general, we can divide patellar fixation in three types: anchors, bone tunnels, and suture techniques, as suggested in the systematic review by Kang et al.[37] They found no differences among them regarding Kujala scores, redislocation rates, and complications. On the other hand, many authors have found more complications related to the use of patellar bone tunnels, especially patellar fractures, and persistent pain.[17] [20] [21] [22] [23] [24] [25] [38] [39] Desai et al.,[1] in their systematic review, showed rates of patellar fractures between 0% and 17%, significantly higher in bone tunnel techniques, despite the fact that the clinical outcomes are similar to those of cortical fixation techniques. The risk of fracture increases as the tunnel size increases, especially for those > 4.5 mm, as seen with EndoButton techniques. Nonetheless, no fractures were reported with tunnels < 3 mm.[1] [25] Our technique addresses this concern by using a small, oblique 1.5-mm perforation only for the passage of needles, and no fractures were found in the present study.

Transosseous suture fixation has shown adequate fixation strength in biomechanical testing in cadaveric models, and a maximum load to failure (540 ± 160 N) stronger than that of the native MPFL and of other fixation methods (anchor, interference screw, transpatellar bone tunnels or medial bone bridge).[16] [18]

To our knowledge, no clinical studies have reported this technique nor clinical results of two-bundle MPFLR with patellar transosseous fixation.

A remarkable advantage of the technique described with transosseous sutures is its low cost, which avoids more expensive implants in the patella, such as anchors, screws, or suspension buttons.

Other complications of MPFLR published among systematic reviews are a postoperative positive apprehension sign between 3.6% and 8.2%, and a reoperation risk between 3.1% and 4.2%.[25] [31] We found 2 cases (6%) with apprehension sign after surgery, and no revision surgery was needed.

Patellar instability involves a wide variety of anatomical abnormalities that make the patella prone to dislocation, such as trochlear dysplasia, patella alta, the TT-TG, and patellar tilt, which have been considered major risk factors for recurrence.[11] [29] The current literature supports associated procedures in patients with demonstrated major risk factors and recurrent lateral dislocation, such as J sign with severe trochlear dysplasia, lateralization of the tibial tuberosity with TT-TG longer than 20 mm, patella alta with a Caton index higher than 1.2 to 1.4, and severe alignment abnormalities (severe genu valgus or femoral anteversion higher than 30°).[40] [41] [42] [43] [44] In this setting, tibial tubercle transfer plays a role when considering correction of abnormalities such as patella alta or an excessive TT-TG. Magnussen et al.,[44] in their systematic review regarding tibial tubercle distalization in patients with patella alta, report that this procedure is safe and effectively reduces recurrent patellar dislocation, with an overall risk of redislocation of almost 2%, with good to excellent functional outcomes.[44] When considering TT lateralization, in a systematic review, Boutefnouchet et al.[43] reported that the literature is sparse and heterogeneous, and a surgical threshold, such as the one for TT-TG alone, could not be determined.[43] In 1994, Dejour et al.[11] used a cutoff point at 20 mm; nevertheless, 20% of asymptomatic knees exceeded that value. This is similar to what is reported by Caplan et al.;[45] therefore, with the current evidence the TT-TG measurement should be used with caution and in combination with other findings to decide whether the surgical correction is necessary.[11] [43] [45]

Mulliez et al.,[46] in a study with 129 patients, found no differences when comparing the functional results between isolated MPFLR (91 patients, 70%) and MPFLR associated to tibial osteotomy (38 patients in the group, 30%) in patients with TT-TG longer than 20 mm and Caton index higher than 1.2.[46] According to our protocol, 11 (32%) of our patients had indication for osteotomy, but, because of open physis in 4 of them, we finally performed an associated osteotomy in 7 (20%) cases, and did not find differences in functional results, dislocations or complications. We must be aware that these two groups are not entirely comparable because of the higher grade of abnormal anatomical factors in the osteotomy group; still, the results showed no significant differences.

The limitations of the present study are the following: the small sample size (34 patients), which can affect the comparison of groups, and a longer follow-up is required to assess the long-term efficacy of this technique, even though the vast majority of studies found in the literature share both of these problems. Another limitation is heterogenous groups of patients with different grades of osseous abnormalities and associated procedures, which could limit the generalization of the technique. Finally, the rate of non-reachable patients was of 23%, which is comparable to what is found in the literature.[1] [31] [47]

Conclusion

Reconstruction of the medial patellofemoral ligament using patellar fixation with transosseous sutures showed excellent functional outcomes, with an acceptable rate of return to sport in the midterm, with no cases of redislocation with a follow-up of 1 to 6 years. The surgical technique described is safe and could avoid possible complications related to the use of patellar tunnels, as well as the morbidity and additional costs related to the use of implants.

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