BLOG: A wider perspective on defending lateral release – What is lateral release?
A rational discussion of any topic requires a clear definition of terms.
My definition of a lateral release is: the sectioning of an excessively tight lateral retinaculum from the level of the joint line up to, but not including, the vastus lateralis muscle or tendon that will allow normal medial translation of the patella into the trochlea. At the other end of the spectrum are authors who define a lateral release as a sectioning of the lateral retinaculum, including the vastus lateralis if necessary, until the patella can be tilted up to a 90° angle.
To be clear, this commentary is not meant to advocate that all, or even most, cases of patellar instability should be treated by isolated lateral release (ILR). Rather it is to encourage the treatment of each such patient as an individual. Just as one should never advise using ILR for all patellar instability cases, one should not follow the dictum that a lateral release has no place in the treatment of patellar instability. A thorough history, physical examination and routine radiographs will reveal a cohort, admittedly small, of patients who have a tight lateral retinaculum as the major cause for instability and who have little or no interest in aggressive or competitive sports. These patients will benefit from a minimally invasive and properly done ILR, which does not preclude more invasive surgery if needed. There are a few competitive athletes who might choose an ILR to delay more definitive surgery until after they reach a certain goal or finish a season.
As the first to publish the use of the lateral patellar release to treat patellofemoral disorders in an English language journal (1974), I need to offer a wider perspective about the recently published study by Tan and colleagues.
Results
It is just by chance that the recently published study by Tan and colleagues of 198 cases demonstrated similar results compared with our preliminary report done 46 years ago. They reported 170 (85.9%) cases that had an isolated lateral release avoided further dislocations. In our 1974 preliminary report, we graded our results differently: 17 of our small sample of 20 cases (85%) graded excellent or good and three (15%) were poor, ie, not improved by the surgery. None were made worse. About half (nine) of our cases had the surgery for recurrent patellar dislocation and none experienced another patellar dislocation within our admittedly too short follow-up period. The remainder were done for anterior knee pain, or “chondromalacia patellae” as it was called then. Certainly, a longer follow-up would have discovered more dislocations.
Re-dislocation rate
To criticize the Tan study for the 14.1% who dislocated and required further surgery ignores the great majority, 85.9%, who successfully avoided further dislocations and surgery. Comparing the re-dislocation rate with medial patellofemoral ligament reconstruction (MPFLR) is fair, but ignores that MPFLR has its own well-defined complication rate and should be avoided if there is a simpler solution. Furthermore, in 1974 and for several years thereafter, the alternative to a lateral release was either a Hauser procedure or Jack Hughston’s “three-in-one” reconstruction (lateral release, medial reefing and medial tuberosity transfer), which was gaining popularity.
Surgeons should always select the least invasive, safest procedure that has the best chance of helping that individual patient rather than relying on statistical evidence from a large cohort of patients who have the same diagnosis, yet whose signs and symptoms may be caused by various and different abnormalities. All patients with patellar instability are not the same.
Biomechanical rationale
A biomechanical rationale for releasing the lateral retinaculum has always been to release the excessively tight lateral retinacular tether, which prevents the patella from moving medially to engage the trochlea with better congruence. If the retinaculum is not tight, it should not be released. Presumably, the lateral retinaculum contracts and tightens following the initial patellar dislocation or when an extensor mechanism misalignment causes a chronic lateral subluxation.
Amis performed his biomechanical studies to learn which anatomic structures contributed to lateral patellar instability using cadaveric knees. He applied a lateralizing force to a cadaveric patella and began sectioning the medial structures sequentially. Then, he created a pseudo-dysplastic trochlea in the cadaveric knee using osteotomies. The final restraint from further lateral translation was the lateral retinaculum which he sectioned last. By assigning a proportional value to each sequential step, he calculated that the lateral retinaculum contributed the final 10% of restraint to increased lateral translation of the patella.
So, yes, the lateral retinaculum does contribute 10% to lateral stability, but only the final 10%, not the first or second. If loss of lateral stability is a concern, perhaps the more simple and safer mesh lengthening should be performed, rather than a layered lengthening of the lateral retinaculum.
Complications
After the 1974 publication and subsequent lectures about the lateral release, it became a popular operation, especially with the introduction of arthroscopic surgery — perhaps, too popular. Our larger follow-up study about proper indications and longer-term results received multiple rejections (a disadvantage of private practice). Some surgeons, such as Henry and colleagues (1986), reasoning that “if a little is good, a lot would be better,” published criteria (the “90° turn-up test”), which can lead to over-release and medial patellar instability. See Pagenstert and colleagues, 2012. Others performed a lateral release for the wrong indications, releasing an already normal or loose lateral retinaculum. Therefore, it was not surprising that 14 years after our preliminary report, Jack Hughston published his study of 54 cases of over-release leading to iatrogenic medial instability. To avoid iatrogenic medial patellar instability after a lateral release, see Sanchis-Alfonso and Merchant, 2015.
Conclusion
As patellar instability has multiple causes, such as trochlear dysplasia of varying severity, increased standardized Q angle and increased TT-TG distance of different amounts, patella alta of differing ratios, variable level of triggering physical activity, etc., each patient deserves a thorough history and physical examination to allow the surgeon to advise the patient about the safest operation with the best chance of success given his or her current and future physical activity level.
References:
Healy WL, et al. J Bone Joint Surg Am. 2003;doi:10.2106/00004623-200310000-00007.
Healy WL, et al. J Bone Joint Surg Am. 2004;doi:10.2106/00004623-200409001-00009.
Henry JG, et al. Am J Sports Med. 1986;doi:10.1177/036354658601400205.
Hughston JC, et al. Am J Sports Med. 1988;doi:10.1177/036354658801600413.
Merchant AC, et al. Clin Orthop Relat Res. 1974;doi:10.1097/00003086-197409000-00027.
Merchant AC, et al. Knee. 2020;doi:10.1016/j.knee.2020.03.001.
Pagenstert G, et al. Arthroscopy. 2012;doi: 10.1016/j.arthro.2011.11.004.
Sanchis-Alfonso V, et al. Arthroscopy. 2015;doi:10.1016/j.arthro.2015.01.028.
Senavongse W, et al. J Bone Joint Surg Br. 2005;doi:10.1302/0301-620X.87B4.14768.
Tan SHS, et al. J Knee Surg. 2020;doi:10.1055/s-0039-1688961.
Collapse