Evaluating joint space widening and clinical outcomes after medial collateral ligament pie-crusting: All-inside versus outside-in techniques

INTRODUCTION

Arthroscopic management of medial meniscal tears frequently requires adequate visualization and access to the posteromedial compartment.^[1] In cases where the medial joint space is insufficient, controlled release of the medial collateral ligament (MCL), commonly referred to as “piecrusting,” is a well-established adjunct to improve working space without compromising joint stability.^[2] This technique involves percutaneous or arthroscopic puncturing of the superficial MCL fibers using a needle, enabling incremental valgus laxity for instrumentation and meniscal repair.^[3]

Two principal approaches to MCL pie-crusting (PC) are currently practiced: The all-inside arthroscopic technique and the outside-in percutaneous technique.^[3,4] The all-inside method offers the advantage of direct visualization, potentially allowing more controlled fiber release, while the outside-in approach is technically simpler and avoids intraarticular instrumentation for ligament release. However, concerns remain regarding the degree of joint space widening, postoperative stability, and long-term functional outcomes associated with each method.^[3-5]

Although prior biomechanical and cadaveric studies have demonstrated the effectiveness of PC in increasing medial joint space, there is limited high-quality clinical evidence comparing the two techniques in live patients.^[6] Furthermore, the correlation between the magnitude of joint space widening and patient-reported outcomes, such as pain relief and functional recovery, remains incompletely understood.^[7]

The present prospective comparative study aims to (1) quantitatively assess medial joint space widening achieved with all-inside versus outside-in MCL PC during arthroscopic procedures, and (2) evaluate post-operative clinical outcomes, including pain, knee function, and stability. We hypothesize that both techniques will produce comparable improvements in joint space and clinical recovery, with no significant compromise in medial stability.

MATERIALS AND METHODS

Surgical procedure and PC techniques

Diagnostic arthroscopy

All patients underwent standard diagnostic arthroscopy through the anterolateral portal. A valgus force was applied to the knee to assess medial compartment tightness. Intraoperative fluoroscopic images at 100% magnification were obtained to measure the medial joint space before PC. All fluoroscopic images were taken at 30° flexion under valgus stress by the same surgical assistant.

All-inside technique (Group A)

A 30° arthroscope was introduced through the anterolateral portal to visualize the posterior horn of the medial meniscus. Through the anteromedial portal, an 18-gauge needle was used to perform multiple punctures of the deep MCL fibers under direct visualization, beginning at the posterior-most portion of the ligament just anterior to the menisco-synovial junction. Valgus stress was applied incrementally during the procedure to achieve controlled lengthening of the MCL [Figure 1].

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Figure 1:

Arthroscopic images of the all-inside technique. (a) Medial joint opening before piecrusting, (b) 18-gauge needle puncturing the multiple sites of the deep medial collateral ligament under direct visualization, (c) Medial joint opening after pie-crusting.

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Outside-in technique (Group B)

Percutaneous MCL release sites were marked approximately 1.5 cm posterior and slightly distal to the medial epicondyle. Transillumination through the arthroscope ensured accurate needle positioning. An 18-gauge spinal needle was inserted percutaneously at the marked site, and multiple punctures of the superficial MCL were performed while applying a continuous valgus force to the knee. The needle was oriented anterior-to-posterior and withdrawn in a controlled manner to release the ligament fibers gradually [Figure 2].

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Figure 2:

Arthroscopic images of the outside-in technique. (a) Medial joint opening before piecrusting, (b) arthroscopic light illumination, and (c) puncturing the multiple sites of the deep medial.

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After PC, the medial joint space was re-measured under fluoroscopy with valgus stress applied at the same magnification.

Outcome measures

An independent observer, blinded to the PC technique, documented all outcomes preoperatively and at follow-up visits. The observer was blinded to group allocation during clinical follow-up. The following data were collected.

Demographic and baseline data

Age, sex, side involved, associated injuries, medial meniscus tear location, and Beighton score. Intraoperative joint space opening: measured on fluoroscopic images before and after MCL PC.

Post-operative swelling

Graded on a 0–3 scale: Grade 0: No swelling or bruising, normal knee movement; Grade 1: Mild bruising, minimal soreness, knee movement normal; Grade 2: Moderate swelling and pain, limited knee flexion; Grade 3: Severe swelling, significant pain, restricted knee motion.

Postoperative medial joint laxity

Evaluated on valgus stress test at 30° knee flexion, graded as: Grade 0: <3 mm opening; Grade I: 3–5 mm; Grade II: 5–10 mm; Grade III: >10 mm.

Pain assessment

Visual Analog Scale (VAS, 0–10) at the immediate postoperative phase, 2-week, and 6-week follow-up.

RESULTS

A total of thirty patients were analyzed in this study, with 15 patients in the all-inside group (Group A) and 15 in the outside-in group (Group B). The mean age of patients in Group A was 38.93 ± 14.53 years, compared to 47.26 ± 13.23 years in Group B, with no statistically significant difference between the groups (P = 0.124). There were no significant differences in gender distribution, side of involvement, associated injuries, tear location on the medial meniscus, or Beighton scores, indicating that the baseline demographic and clinical characteristics were comparable between the two groups [Tables 1 and 2].

Intraoperative measurements of medial joint space before PC revealed mean values of 4.2 ± 0.83 mm in Group A and 3.93 ± 0.67 mm in Group B, with no statistically significant difference (P = 0.361). After PC, the medial joint space increased to 8.5 ± 1.25 mm in Group A and 9.2 ± 0.97 mm in Group B; this difference also did not reach statistical significance (P = 0.129). However, when analyzing the magnitude of joint space widening, the increase was 4.4 ± 1.14 mm in Group A and 5.26 ± 1.12 mm in Group B, reflecting a larger, though statistically non-significant, expansion in the outside-in group (P = 0.526) [Table 3]. Post-operative evaluation revealed notable differences in early outcomes between the two techniques. At the immediate post-operative phase, the outside-in group exhibited higher medial knee swelling, with several patients demonstrating grade II and III swelling, whereas most patients in the all-inside group exhibited grade 0 or I swelling. This difference was statistically significant (P = 0.001). Similarly, postoperative pain measured using the VAS was higher in the outside-in group immediately after surgery (P < 0.001) and at the 2-week follow-up (P = 0.026). By 6 weeks postoperatively, VAS scores had decreased substantially in both groups, with no significant difference observed between them (P = 0.242) [Table 4].

Assessment of medial joint laxity on valgus stress testing demonstrated that the outside-in group had greater laxity in the immediate post-operative phase (P = 0.020) and at the 2-week follow-up (P = 0.013). By the 6-week follow-up, however, the degree of laxity was similar between the two groups (P = 0.143), indicating recovery of medial stability over time [Table 4].

Overall, these results indicate that while both all-inside and outside-in MCL PC techniques effectively increase medial joint space, the outside-in technique is associated with greater early postoperative swelling, pain, and transient joint laxity. By 6 weeks postoperatively, however, clinical outcomes, including pain, swelling, and medial stability, were comparable between the two groups.

DISCUSSION

To our knowledge, this study is among the first prospective comparative clinical investigations directly evaluating all-inside versus outside-in MCL PC in live patients undergoing arthroscopic medial meniscus repair, providing novel insights into joint space widening and short-term functional outcomes. The goal of this research is to compare the two different approaches to PC the MCL, which is used to provide a wider joint space and a simpler arthroscopic operation by acting as an adjuvant for valgus during the medial compartment arthroscopic intervention at the knee. In the last 10 years, a relatively novel technique called “piecrusting” has been used mostly in total knee arthroplasty for genu valgum during the lateral soft tissue release phase.^[8] Consequently, a few knee replacement surgeons have begun advocating for the application of a PC method to treat varus anomalies and release the MCL.^[9] The best accessibility and visibility for meniscal pathology diagnosis and therapy have been achieved recently with the application of MCL pie crusting.^[10]

In individuals with tight medial compartments, it can be difficult to access the posterior horn of the medial meniscus.^[11] PC, the MCL helps visualize this area. Iatrogenic chondral injury may occur in these cases due to the limited medial joint space generated by the anterior arthroscopic procedure.^[12] Dick et al.’s research of 3714 arthroscopic procedures revealed that iatrogenic articular cartilage was common, with a frequency of 2%.^[13] Animal experiments by Klein and Kurze concluded that arthroscopically created articular lesions did not heal.^[14] The PC approach allows for improved medial joint space, enough visibility of the medial meniscus, and the insertion of arthroscopy instruments without causing chondral injury.^[4]

Based on evidence from the literature, there are presently two types of PC release procedures for the MCL after arthroscopic medial meniscus surgery: the Inside-out methodology and the outside-in approach.^[4,5] By fully releasing the deep MCL, the all-inside approach provides direct viewing of the posterior horn with the least amount of joint space.^[12] Although the procedure does not involve skin penetration, possible disadvantages include restricted instrument access because of intra-articular structures. In patients with constricted medial compartments, this approach allows for an adequate working area, although it requires careful control through the anteromedial portal.^[4,15] Conversely, the outside-in approach uses percutaneous MCL needle punctures to expand the medial tibiofemoral joint area. However, it can cause several skin punctures, necessitate further maneuvers to precisely pinpoint the needle site, and be uncomfortable for patients due to the potential severance of the saphenous nerve or superficial MCL.^[3,5] In this study, the effects of PC of MCL on intraoperative joint space opening, post-operative swelling, laxity, and knee discomfort are compared and analyzed with respect to these two distinct procedures.

The clinical findings clearly show that PC release of the MCL can increase the visual field of the posteromedial area of the knee joint.^[11] However, the answer is still not clear to the question of whether the all-inside or outside-in technique provides a more expansive medial joint space opening. In the study by Fakioglu et al., medial joint space widening on valgus stress radiographs following outside-in PC was measured at baseline and following surgery.^[16] The median joint space width was 7.1 mm before surgery and 9.1 mm following it.^[16] Zhu et al. measured 6.8 mm following PC and 4.3 mm before surgery.^[17] Roussignol et al. reported an increase from 4 mm pre-operatively to 7.9 mm post-PC. In the same way, the research used all-inside PC arthroscopic procedures.^[18] According to Han et al., following arthroscopic all-inside PC, the radiographic joint space widened from 5.9 ± 0.8 mm preoperatively to 9.2 ± 1.1 mm.^[15] Our research revealed a substantial difference between the two approaches, with a mean difference of 4.4 ± 1.14 mm for the medial joint space opening in the all-inside technique and 5.26 ± 1.12 mm for the outside-in technique. It implies that when compared to the all-inside technique, the outside-in technique has more joint space opening.

After the PC release of the MCL, knee stability was mostly associated with the following variables: This procedure only penetrated the posterior MCL and POL, leaving the front section of the MCL intact.^[15] In addition, the functional deficiency of the transected MCL was made up for by the remaining components, especially the anterior cruciate ligament, following PC of the MCL.^[19] A clinical investigation was carried out to examine joint space opening. A few of these clinical trials additionally evaluated the amount of time that passes after this percutaneous release before the medial joint space opening stabilizes. A subjective impression of medial instability of the knee was not felt throughout follow-up, according to the majority of studies, and the MCL injury was grade I with <5 mm opening on the medial side in the valgus position with 20° flexion immediately after operation, but negative after 6 weeks.^[15,16] When a clinical examination was conducted outside with a PC, all patients in the study by Fakioglu et al. demonstrated an opening of <5 mm with a specified endpoint when compared to the contralateral limb.^[16] On average, this extra laxity on clinical evaluation was gone in 3.5 weeks.^[16] Six months after the procedure, Claret et al. found that none of the seventy patients who had the MCL released percutaneously had laxity on inspection.^[20] Three months following the operation, Han et al. found neither subjective nor objective medial instability of the knee joint.^[15] In our study, there was a noteworthy distinction in laxity between the 2-week follow-up and the immediate post-operative period in our investigation. At the same time, the outside-in PC’s had a larger degree of laxity than the all-inside. At the 6-week follow-up, the laxity was similar between the two groups, nevertheless, suggesting that the difference is only present in the short term and not in mid- to long-term follow-up.

In addition to a recent systematic review, numerous trials have demonstrated the safety of controlled percutaneous MCL release, showing no signs of saphenous neurovascular injury, subjective patient instability, significant post-operative MCL laxity on stress images, or post-operative pain.^[7] Subjective instability, post-operative pain, and the possibility of local consequences such as hematoma or neurovascular injury are insignificant when using the entire inside MCL PC method.^[7,10,16] In addition, in our investigation, the outside group had considerably more post-operative swelling on the medial part of the knee. In the immediate post-operative phase and the 2-week follow-up, there was also a higher VAS score in the outside method. At the 6-week follow-up, there was, however, no discernible difference.

These findings indicate that both all-inside and outside-in MCL PC techniques are safe and effectively facilitate arthroscopic access to the medial compartment. However, the outside-in approach is associated with higher early postoperative pain, swelling, and transient medial laxity. Surgeons should consider these short-term differences when selecting the technique, tailoring the approach based on intraoperative visualization requirements and patient comfort, while expecting similar outcomes by 6 weeks postoperatively.

There are some limitations for this study. First of all, the small sample size and absence of a formal power analysis limit the statistical power of the study and may affect the reliability of conclusions regarding equivalence between all-inside and outside-in MCL PC techniques. Second, the study uses the fluoroscopy image with the same magnification to calculate medial joint space widening. Although the surgeries were performed by the same surgeon, the variation of joint space might be seen according to the valgus force applied by the assistant, and the side of intervention where more force can be given, using a dominant hand. Third, the post-operative laxity was measured and graded based on clinical examination only; no standardization of gap opening measurement was done. Fourth, due to our low subject count and short follow-up period, additional patients need to be recruited with a longer follow-up time. Fifth, the interobserver reliability was not assessed. Furthermore, other standardized outcome measures of knee function, like the International Knee Documentation Committee/Knee Injury and Osteoarthritis Outcome Score, were not included for analysis. It will be convincing to embark on a high-quality randomized-controlled study in which comparison groups using an alternative PC technique for meniscal visualization are included.

CONCLUSION

Both all-inside and outside-in MCL PC techniques effectively increase medial joint space and facilitate arthroscopic access to the posterior horn of the medial meniscus. Although the outside-in approach produces slightly greater joint space widening, it is associated with higher early post-operative pain, swelling, and transient laxity. By 6 weeks, these differences resolve, and clinical outcomes are comparable between techniques. These results indicate that both approaches are safe and effective, and the choice should be guided by intraoperative visualization needs and early postoperative patient comfort. PC thus represents a valuable adjunct in arthroscopic medial meniscus repair, enhancing visualization while preserving long-term knee stability.