Retrospective Study
A retrospective study was performed on the medical records of 715 patients who previously underwent surgery between 2018 and 2023. 834 surgeries were performed with 119 making up bilateral (both legs).
Of the total surgeries, 92.40% were determined to have obtained a successful outcome, 5.40% were unsuccessful, and 2.20% were labeled as equivocal. The below tables outline the surgical outcomes as well as the categorical outcomes for the unsuccessful cases. There was a 6.80% infection rate and a 19.60% opposite limb tear rate.
The average patient weight is 70 lbs. with 47% of patients over 70 lbs and the average age is 8 years with 30% of patients 10 years and older.
Determining The Point of Final Assessment for Surgical Outcome: Final Point of Contact
In the retrospective review of the 834 MFLS surgical procedures the goal for most accurately assessing the outcome from MFLS surgery was to follow the status of each patient as long after surgery as was possible, up to and including communication with the client/owner at approximately one year after surgery. MFLS surgical patients were scheduled for re-evaluation at 2 weeks after surgery and 8 weeks after surgery for “required” visits and assessments. Clients/owners were also asked to schedule a “recommended” visit for reassessment of each MFLS surgical patient at 6 months after surgery for the purpose of clearing the patient to resume normal or regular activities.
The final point of determining each case outcome assessment status varied from patient to patient. As a rule of thumb however, the final case outcome assessment status was taken to be the patient’s assessed status at the time of the last in hospital physical examination; or in some cases when continued contact and communication with the client/owner was possible, the last and best assessment status communicated to us by the client/owner was used as the final case outcome assessment status.
As MFLS surgeries were performed for clients/owners from all over New England on a daily basis and from all over the country on a regular basis, those clients/owners traveling greater distances were often re-evaluated locally by their regular veterinarians and pertinent assessment information was then requested to be provided by the client/owner and/or local veterinarian at the aforementioned intervals. Further contact and updates were requested from client/owners at approximately one year after surgery for the client/owner’s own subjective assessment of the patient’s status, which included the patient’s level of comfort and function, but client/owner compliance was quite variable. Client/owner compliance was a key and essential requirement for fulfillment of these assessment goals, and client/owner noncompliance was a factor at all points of patient reassessment over time.
In cases of client/owner noncompliance—in terms of failure to either show up for a scheduled or recommended visit for reassessment and/or failure to communicate and respond to our attempts to communicate with them regarding the patient’s status at any given point in time—the assessed status of the patient was then assumed to be the same status as the last in hospital assessment or, if a further assessment was communicated after the last in hospital assessment, the last assessed status communicated to us by the client/owner.
Criteria for a Successful Outcome From Surgery
In establishing the criteria for a successful outcome from surgery, client/owner noncompliance as it pertains to the recommended in-office examinations and assessments and/or basic contact and communications with the hospital was an issue in some cases. When there was cases involving client/owner noncompliance and failure to show or communicate, it was deemed to be reasonable and justifiable to presume that “no news is good news” and there was a very high likelihood or probability that the patient was doing well and the outcome from MFLS surgery was favorable.
Assuming that the vast majority of clients/owners are responsible and concerned pet owners, in instances of client/owner noncompliance and failure to communicate this “no news is good news” mindset was determined to be the most appropriate, sensible, and accurate designation for assessment of the patient’s status and the surgical outcome. In the absence of information to the contrary, the only assumption being made was that the vast majority of clients/owners are responsible and concerned pet owners and would be in contact if they had any real concerns.
It was deemed to be self-evident and just common sense that if the patient were not doing well and/or there were any significant concerns on the part of the client/owner, it would be reasonable and obvious to assume with a high degree of certainty that a responsible and concerned client/owner would then naturally effort to show up for a recommended appointment (or seek medical care at the hospital without an appointment, or elsewhere) and/or initiate contact with the hospital by phone or email, and would certainly respond to our attempts and efforts to contact them in order to have their pet’s health issue and their own concerns addressed and resolved.
In the vast majority of surgical cases clients/owners were compliant and in contact with the hospital and the criteria for a successful outcome from any given MFLS surgery was based on several factors. The data analysis sheet of the retrospective review of the 834 MFLS surgical procedures highlights several potential post-operative complications and diagnoses that factored into and aided in determining the overall success or failure of a surgical outcome. Merely experiencing a complication or having been diagnosed with a post-operative issue was not the basis for determining success or failure of a given surgical procedure, as resolution of these issues and complications would in the majority of cases ultimately allow for a positive or successful outcome. Rather, the overall recovery and level of function attained by the patient from about 6 months to 12 months after surgery was the primary factor in allowing confident determination of the success or failure of a given surgical procedure. In cases where the client/owner was eventually noncompliant and failed to continue communications at some point, the overall recovery and level of function attained by the patient at the last available point of contact with the client was the primary factor in allowing a confident determination of the success or failure of a given surgical procedure.
Overall, each patient’s final assessed status in terms of success or failure of the surgery was determined by and considered to be the status held at the last point of contact with the client. Given the only assumption that the vast majority of clients/owners are responsible and concerned pet owners, it was determined that most (if not all) clients/owners would be in touch and communicating with the hospital if the patient were experiencing any significant problems or issues that raised genuine concerns. Furthermore, so long as the patient was doing well during their recovery from surgery and at the point of last contact with the client/owner and in the absence of information to the contrary, it was deemed most appropriate, sensible and accurate to designate the final assessed status of the patient and the assigned surgical outcome as a positive or successful outcome. The same is true of the alternative or negative outcome – if the patient was not doing well at the point of last contact with the client, the case was considered to have a negative or failed outcome.
As a general rule of thumb, if a given case had a “questionable” outcome that could not unequivocally be classified as a successful outcome, it was then automatically assigned a negative outcome status. There were however a small number of cases that ultimately were classified as “Equivocal” outcomes. In these cases it was evident that there was conflicting information—both positive and negative factors—that portrayed or represented a subjective gray area and made the ultimate outcome from surgery debatable – wherein one could make a case for both a positive outcome and a negative outcome. It was determined that this conflicting information precluded the ability to fairly, accurately, and unambiguously determine a positive or negative outcome from surgery.
As the result of pre-existing conditions that were present in many patients prior to surgery, a wide range in age of surgical patients, variations in pain tolerance among individual patients and variations in client/owner compliance with post-operative care protocols and rehabilitation regimens, the overall recovery time and requirements for rehabilitation varied throughout all patients. The percentage of the time owners reported patients were using their surgically repaired limb by 6 to 12 months post-op was also found to be variable. The vast majority of patients determined to have successful surgical outcomes were fully weight-bearing on and consistently using the surgically repaired limb 100% of the time by 6 months post-surgery. A small percentage of patients determined to have successful surgical outcomes were considered as doing well and showing progress and reported to be consistently using the surgically repaired limb less than 100% of the time but no less than 75% of the time by 6 months post-surgery or at the point of last contact with the owner. A small minority of patients having successful surgical outcomes required a more extended period of recovery and were fully weight-bearing on the surgically repaired limb by no later than 1-year post-surgery. No patients using the surgically repaired limb less than 75% of the time by 6 months post-surgery or at the point of last contact with the owner were considered to have a successful surgical outcome. Since no two post-operative recoveries are the same and various issues may present themselves during the patient’s recovery that make any given recovery unique in some way, it is not surprising that the weight-bearing percentage at various points in recovery for each patient varied case by case. It is noteworthy that many patients who were not fully weight-bearing 100% of the time at different points in their recoveries often had either pre-existing conditions, and/or suspected meniscal injuries.
With the objective of most accurately assessing the outcome from surgery, in the retrospective review of the 834 MFLS surgical procedures the data analysis scrutinized how each patient recovered from any post-operative issues or complications, as well as any pre-operative issues or conditions that may have been present and potentially affected the post-operative recovery and surgical outcome of a given patient. Specifically, these post-operative issues or complications were categorized as (1) soft tissue injuries, (2) surgical site infections (SSI), (3) same limb meniscus tears, (4) opposite limb CrCL tears, (5) medial luxating patella (MLP) issues, and (6) tick-borne infections, (7) low pain tolerance of the patient. For clarification, these post-operative issues or complications are not specifically related to or correlated with the MFLS surgical procedure, these post-operative issues or complications may occur after any of the commonly performed CrCL surgical repair procedures for dogs. Pre-existing conditions that can also affect post-operative recovery include (1) osteoarthritis, (2) obesity, (3) acute or chronic tick-borne illnesses, (4) opposite limb CrCL tears, (5) muscle atrophy, (6) concurrent or subsequent meniscal injuries secondary to the primary CrCL tears, (7) hip dysplasia, and (8) advanced age of the patient, (9) extended or prolonged period of injury, and (10) medial luxating patella issues.
At 6 months post-op the vast majority of MFLS surgery patients were consistently fully weight-bearing on the surgically repaired limb as determined on examination and observation of the patient and/or reported by the owner/client. For the purposes of this study, consistently fully weight-bearing was defined as using the surgically repaired limb 100% of the time. However, as no two surgical recoveries are the same and recovery from surgery for every patient is a process that happens over a variable period of time – as an example, older patients in general are going to require more time for healing during their recovery and are also more likely to have one or more pre-existing conditions they must deal with and overcome – some patients having pre-existing conditions and/or post-operative issues or complications that were progressing and variably fully weight-bearing from 100% of the time to no less than 75% of the time during their recovery (by the owner/client’s own assessment), were considered to be consistently fully weight-bearing overall during their recovery.
Some other patients that would eventually or ultimately be classified as successful outcomes may not have been consistently fully weight-bearing on the surgically repaired limb at 6 months after surgery as determined on examination and observation of the patient and/or as reported by the client/owner, but were progressing and still in the process of healing from post-operative issue(s) or complications and/or pre-existing conditions. Many patients that were dealing with soft tissue injuries after surgery – most typically meniscal injuries or tendonitis (patella or iliopsoas) of the surgically repaired limb – were assisted in their recoveries by being placed on Multi-Modal Pain Management Protocols that helped the patient overcome difficulties in recovery related to pain and inflammation, facilitating an easier and faster recovery.
At 1 year after surgery, the vast majority of patients designated as having successful MFLS surgical outcomes were consistently fully weight-bearing 100% of the time. Some patients at 1-year post-op may still be recovering from soft tissue injuries (like meniscal tears), they however have no issues with the surgical repair itself and their stifles are completely stable, so these patients are deemed to have a successful MFLS surgery outcome.
Criteria for Non-Successful Outcome
MFLS surgeries that did not have successful outcomes made up 5.4% of the data analysis. The criteria for having a non-successful outcome included: (1) patients having persistent lameness at over 50 days post-op, (2) patients that are not fully weight bearing (patients that are fully weight bearing less than 50% of the time by the 6-month mark, with no diagnosis or cause for lameness), and (3) patients that show no improvement with multimodal pain management protocol medications.
A non-successful surgical patient at 1 yr post-surgery has a non-resolved lameness and is fully weight-bearing less than 50% of the time. These patients may have persisting chronic inflammation of the surgically repaired stifle area. Some of these patients may be experiencing a significant and prolonged on-going immune reaction to the implants that may eventually constitute rejection of the implants by the patient’s immune system. For patients experiencing these kind of issues that ultimately developed an opening in the skin with drainage in or around the incision site, a culture and cytology of the discharge was typically performed to rule out an active infection. However the majority of these cases that developed a drainage site at this later stage (6 to 12 months post-op or more) did not involve an active infection, and the discharge more typically represented an immune mediated reaction to the implants rising to the level of rejection of the nylon implants. In most cases, these symptoms arising at this later stage indicated that the nylon implants (filaments) must be removed in order to bring a resolution to the strong immune reaction (an over-reaction) and associated inflammation they were continuing to provoke.
Any unresolved or on-going infections (SSI) of the surgically repaired stifle by 6 to 12 months after surgery were considered to be a non-successful surgical outcome, usually as the result the secondary issues associated with the SSI in the stifle affecting the surgical recovery overall. These associated secondary issues included on-going chronic inflammation, tendonitis, muscle atrophy, persistent lameness, and in a small number of more serious cases, sepsis.
Criteria for Equivocal Outcomes
There were a small number of cases (2.2%) that were ultimately classified as “Equivocal” outcomes. Equivocal outcome assessments were assigned to cases when there was conflicting information – both positive and negative factors that taken together, made for a subjective, inconclusive, and debatable end result – and this precluded a fair and accurate determination of a positive or negative outcome. A small number of patients may have been assigned an Equivocal surgical outcome as the result of a lack of information due to owner/client noncompliance and our inability to communicate with the owner/client to obtain sufficient information to objectively determine a positive or negative surgical outcome status and the patient’s post-operative recovery. Medical records and doctors’ notes were always used to assess the patient’s surgical recovery and to indicate the status of the patient, but as the result of owner/client noncompliance, a lack of information in some cases made it virtually impossible to make an accurate and justifiable determination of either a positive or negative surgical result—hence these cases were designated and classified as Equivocal results.
Criteria for Surgical Site Infections
Several factors may indicate a surgical site infection following surgery. The criteria used to confirm a surgical site infection were as follows: (1) a fever of 103 or higher with mild to moderate swelling, inflammation, and pain, (2) mild to moderate swelling, inflammation, and pain with a discharge at the incision – a sample was then sent for culture and came back with positive bacterial growth results, and (3) an incision site having a purulent discharge from the incision site will also confirm a surgical site infection (Overesch, 2023). A major surgical site infection results in sepsis, or in removal of the surgical implants to resolve the infection (Overesch, 2023).
Criteria for an Amended Surgical Repair constituting a Surgical Complication
Patients who presented with lameness after surgery associated with excessive physical activity prior to 6 months post-op that resulted in disruption of the structural integrity of the surgical repair and consequent instability of the stifle joint, requiring amended (MFLS) surgery to re-stabilize the stifle joint were assigned this designation. Disrupted MFLS surgical repairs were typically the result of client/owner (and/or patient) noncompliance as it pertained to surgery recovery protocols requiring restricted, slow, and controlled use of the surgically repaired limb and slow controlled patient activity overall for the first 6 months after surgery. An amended surgical repair is considered a complication after surgery.
Criteria for Surgery to Remove Implants or Prostheses (Filaments) as a Complication
Prolonged and significant inflammation of the surgical site with intermittent lameness that does not resolve may not in fact be related to a surgical site infection (SSI), but rather may be consistent with and indicative of a significant and prolonged immune-mediated reaction to the surgical implants/prostheses. A small number of patients experiencing an overly strong and prolonged immune response (heightened immune reaction) to the nylon implants or prostheses ultimately required surgical removal of these implants or prostheses to allow for greater comfort and use and a full surgical recovery with a more ideal surgical outcome. These patients experiencing an immune mediated rejection of the nylon surgical implants typically have relapsing periods of lameness of undetermined origin and/or experience extended and significant surgical site inflammation that is often exacerbated on days having greater activity. The onset of these symptoms typically ranges between 3 and 6 months after surgery and typically extends throughout the 6-to-12-month post-operative recovery period. By this point in time (6 to 12 months after surgery) sufficient immune provocation has occurred and the biosynthetic union has typically become well established. For most patients by approximately 8 to 10 months after surgery, the immune provoked biosynthetic union has sufficiently fortified the structural integrity of the MFLS surgical repair and imparts enough strength and durability to the surgical repair to allow for – what has then become a necessary – surgical removal of the nylon implants/prostheses.
Surgically removing the nylon implants/prostheses (filaments) from their scar tissue encasement removes the source of continued and excessive immune provocation and so eliminates the resulting and continuous inflammation and discomfort associated with it. Of equal or perhaps even greater importance is what is left behind after surgically removing the encased nylon implants/prostheses – the collagen (scar tissue) encasement that remains in place and intact continues to function as an embedded former “exoskeleton” providing structural integrity and stability as well as constant and consistent isometric tension through the entire range of motion of the stifle joint. As of the date of publication, there has not yet been a patient encountered that did not do well after surgically removing the nylon implants/prostheses (filaments).
Criteria for Soft Tissue Injuries
At various points in time throughout the post-surgical recovery period and the post-surgical recovery process, some individual patients may experience one or more post-operative soft tissue injuries. At the time of their post-operative re-examination visits (2 weeks, 8 weeks, and 6 months post-op), patients may have presented with either acute lameness, pain on flexion and extension, stiffness when rising from recumbence, or may have had audible “clicks” in their surgically repaired stifle joint. Any of these issues, and others, may indicate a post-operative soft tissue injury has occurred.
In the majority of cases these soft tissue injuries resolved with time and proper care, typically managed with restricted activity and various medications if indicated. Most soft tissue injuries experienced during the post-surgical recovery period (and recovery process) ultimately did not impact the overall outcome of the surgery and ultimately the overall use of the surgically repaired limb. The most common and significant injury experienced during the post-surgical recovery period and post-surgical recovery process were (suspected) meniscal tears. For the majority of patients in this study, a non-surgical approach with conservative management of meniscal injuries was the preferred method of treatment. Other common soft tissue injuries included patella tendonitis, MTU (muscle-tendon unit) strains, and iliopsoas tendonitis.
Work Cited
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